After the termination of the railcar project in Romania George Constantinesco returned to the peace and quiet of Oxen House on the shores of Lake Coniston. Here, he was in his element with the beauty of the lakes and mountains and the associations with so many famous writers and artists. He remembered his days at school when his father urged him to balance his education with a study of the arts as well as physics and chemistry. He had taken his father's advice but had little time to devote to cultural activities because of the frantic pace of his work in London and Weybridge, although he did make time to play the piano. He continued to enjoy his piano playing at Oxen House and, encouraged and guided by Eva, took an interest in English literature but his main driving force was still his work and his desire to see his ideas and inventions put into practice.

Unfortunately George did not enjoy robust health. From an early age he had suffered from respiratory and heart weaknesses which restricted his physical activities more and more as he got older. By the time he reached his late fifties he was under doctor's orders not to travel far from home and not to get excited and Eva saw to it that this advice was followed. Within these limitations George threw his skills and energy into new studies and plans for projects. His immediate task was to improve his laboratory and office facilities. The electricity supply needed improvement as there was no mains electricity available in the area during the 1930s. Oxen House had only a small generating plant with storage batteries which would have to be replaced as it was inefficient, smelly and noisy.

On the estate there was a stream about half a mile away which flowed through steep woodland known as Thrang Crag and then out to Lake Coniston. George decided that this would be the source of a hydroelectric power scheme for Oxen House. Estimates provided by a local firm of turbine manufacturers for the installation were regarded as far too expensive. So George, with his usual determination and resourcefulness, designed and constructed the whole scheme himself, which included the manufacture of the turbine in his own workshop, using local materials and labour and the help of his teenage son and stepsons during school holidays.

The scheme included the construction of a stone dam across the stream, the installation of a pipeline from the dam to the turbine house and the installation of about half a mile of overhead power cable from the turbine to Oxen House. The turbine itself consisted of copper vanes set in a reinforced concrete wheel, the mould of which was a large circular biscuit tin. There was a shaft through the centre held on each side in plain bearings continuously supplied with oil from drip feed reservoirs. One end of the shaft was connected through a flexible coupling to the dynamo. The force of water impinging on the turbine blades was controlled by a simple ball cock device to increase or decrease the size of the jet orifice as required to keep the speed of the turbine constant. By this means there was no appreciable fluctuation in the electricity supply; so little in fact that no storage batteries were used. This simple and cheap installation worked continuously for 20 years, with the minimum of maintenance, until mains electricity became available.

Living on the shores of Lake Coniston George observed the various craft plying up and down and noted that most of them were rowing boats or sailing boats which were silent, but a few of them were noisy motor boats which travelled slowly in relation to the power of the engine. He decided to demonstrate, for his own interest and the amusement of the family and the locals that it was possible to propel a large rowing boat silently and much faster than the local motor boats, with an electric outboard motor driving a specially designed propeller. An old starter motor driven by two 12 volt batteries in parallel served admirably as the power source. A boat thus fitted and festooned with coloured lights appeared silently and unannounced on the occasion of a nocturnal regatta for the Coronation of King George VI at Coniston, with no visible means of propulsion. It nosed like a ghost among the revellers and disappeared silently and swiftly into the night back to Oxen House Bay. It was the talk of the village for many months to come, with remarks such as "the Professor's up to his tricks again!''

More seriously, resulting from his friendship with Sir Malcolm Campbell, George had embarked on a detailed mathematical analysis of the hydrodynamics and aerodynamics of alternative high speed water craft. He realized that once again war clouds were gathering in Europe. He believed that high speed craft were urgently needed for Naval operations and general Maritime duties, especially as he knew that the Germans were already working on the design of such craft.

Early in August 1939 Sir Malcolm Campbell had just broken the world water speed record (124.86 mph) held by Car Wood of America by travelling at 141.74 mph in his boat Bluebird on Lake Coniston. However, he was worried that the Americans would soon try to wrest the record away from him and he would need a faster boat to make sure he could maintain the record. Knowing of George's abilities and the fact that he was working on the design of high speed craft, Sir Malcolm asked if he would design for him a record breaking speed boat of some 2,000 hp. George readily agreed especially as this project would fit in with his own plans for a craft capable of travelling at up to or over 200 miles per hour and which he claimed would not only break records, but revolutionize Naval and Maritime operations. He considered that one year would be sufficient time for development with Sir Malcolm's help, but they would need proper financial support. He hinted at the type of craft he had in mind, one which would be capable of travelling smoothly even in a choppy sea with greater acceleration and manoeuvrability than available in existing conventional designs.

On 1 st September 1939 Hitler invaded Poland and this was the signal for the onset of World War II. Obviously the design and construction of Sir Malcolm's proposed new speed boat would have to be shelved for the duration, but George considered it even more urgent now that he and Sir Malcolm should join forces to develop a high speed craft for use by the Royal Navy, particularly for submarine destruction. On September 1st 1939 George had already written to Sir Malcolm on these lines with an impassioned appeal for his help in obtaining approval and financial support from the Admiralty for their joint venture. His concluding remarks indicated his intense desire to place himself entirely at the disposal of the Admiralty in pursuance of the war efforts: ''I am ready to put at the Admiralty's disposal all I have, my gift as inventor, my learning as a scientist, and my skill, experience and achievement as an engineer. If you do the same and bring in your extraordinary initiative, courage and vitality, we must succeed. Lose no time."

Both Sir Malcolm and George made every effort to interest the authorities in their proposed project, but the Admiralty would not move until George provided details of his plans on paper and this he refused to do. The same impasse was reached with the Air Ministry. It seemed impossible to break this stalemate. On the one hand there was an inventor who was fearful of disclosing, at that time, his secret technology which might or might not be taken up by the Government. On the other hand no Government Department could officially commit funds for research in an unknown subject, no matter how competent and respected the inventor might be. During World War I the development of the C.C. firing gear was made possible by the initial efforts of serving officers on their own responsibility and the Government subsequently took it on officially because they were desperately in need of the device. In the case of this proposed high speed craft, none of the Services had requested such a craft, nor felt a desperate need for one at that time.

Previous experience of the Royal Navy with one unconventional form of high speed craft the hydrofoil, had not been encouraging. In 1918, Graham Bell, the American inventor of the telephone, established a world speed record of 61 knots in a Forlanini hydrofoil and this success prompted the British Navy to purchase two of these craft for trials in the early 1920s. Unfortunately they broke up and were destroyed in a heavy gale. Next, the British firm of J. S. White, on the Isle of Wight, had carried out successful tests with a small hydrofoil in the early 1930s. The Royal Navy once again became interested and ordered an experimental model, the MT. 101, which was completed in 1930. Again this model was not rugged enough for the rough handling to be expected in Naval operations and it needed continual and costly repairs. For the time being this ended Naval interest in hydrofoils and they assumed that George's idea for a high speed craft would be just another hydrofoil. In the meantime the Germans had been having considerable success with hydrofoils based on the work of Baron Hands von Schertel and in 1940 construction started on a number of designs for use by the Army and the Navy. (George was well aware of this threat, which is why he was so insistent that something should be done urgently to supersede the potential German capability).

Some officers in the Air Services and other individuals did take a personal interest in George's project. They knew from his successes during World War I, that whatever kind of craft he had in mind it would be more formidable than anything available to the Germans at that time. They were able to obtain an engine on loan for George to use in his experiments and limited funds to help him build a boathouse for a model experimental craft, with a launching railway line to Lake Coniston. Then there were problems with obtaining controlled materials from the Ministry of Supply to enable research and development to continue, but he was unable to get the materials or help he needed. As far as staff is concerned George did not have sufficient funds to pay the salary of an engineer. He had hoped that the Admiralty would supply at least one engineering officer on light duty, but this was not approved. The only other source of assistance would be his son and stepsons, but his son Ian was in the Royal Air Force and his stepsons Richard and Michael were teenagers at school. They were also called up later, but the Government did agree to release Richard to help him with his work towards the end of the War.

Immediately after the war George contacted Sir Malcolm Campbell and offered him the use of his new boat house from which to start his Speed Trials again on Lake Coniston. In July 1946 Sir Malcolm came to inspect George's boat house as to its suitability for his purpose, but found it to be too small and decided to build a temporary timber and canvas shed near Coniston. He tried to get a new Griffin engine from Rolls Royce, but there were so many delays that he had to continue for the time being with his old engine. But for the future he had in mind the use of a jet engine and asked George what he thought about the idea. George considered that there was no reason why a jet engine should not succeed provided that the design of the boat and jet combination was correct dynamically so as to avoid longitudinal and lateral resonance oscillations at high speed. The gyroscopic effect of the engine would also have to be taken into account ''...if the boat starts longitudinal bumps, the gyroscopic reaction is a substantial snaking which will be difficult to correct with the rudder. Your task will be to steer a gigantic spinning top, spinning and sliding on the water! Again pardon me to insist, but really I am very uneasy knowing the tremendous risk you are taking."

Unfortunately Sir Malcolm Campbell died in December 1948 in Reigate, Surrey. His son Donald carried on where he left off and was to break the water speed record several times in a jet powered boat. He was killed travelling at over 300 mph on Lake Coniston in January 1967. After the death of Sir Malcolm Campbell, George's own health began to deteriorate further and without the help and encouragement of Sir Malcolm, nor adequate facilities, George had to abandon further work on his own high speed craft. This craft, which was to be a model for development of an ocean going vehicle upwards of 1,500 tons and capable of speeds around 200 mph would have to be something different from a hydrofoil. The von Schertel VS.6 hydrofoil had attained a speed of 47.5 knots and George knew that the maximum attainable would not be much more than the 61 knots achieved by Graham Bell, with any part of the craft, such as foils in contact with the water. The craft would have to leave the water altogether with the aid of wings when travelling at speed, and skim along the surface a few feet above it and be driven by the thrust of aircraft engines.

George never published his ideas on this kind of craft, but the Russians began trials in 1965 with a machine of this kind named an Ekranoplan. The machine operated at heights of 3.5 to 14m above the surface of the water and had a potential speed in excess of 300 knots. Later versions of these craft based on designs by Bartini and developed by the Russians in the 1970s are called ground gliders and are capable of operating over land as well as water. More recently in the 1980s attention has been focused in Britain on the commercial and military possibilities of these craft and they have been Christened as Wingships by Stephen Hooker, the founder Chairman of the Wingship Society.[12] This is 40 years later than George's original ideas for a craft of this type at the beginning of World War II, and that was an opportunity lost for British Industry to be the leader in this new exciting technology.

Following his disappointments with the high speed water craft project George continued to develop new ideas and inventions. At the same time he disseminated his knowledge of sonics in papers and lectures and encouraged others to apply sonic principles in solving engineering problems. Some of his post war inventions were not necessarily of sonic origin but quite unique. For example in one case he developed a new type of reinforced concrete, which he called Feron. The main innovative factor was the shape and nature of the steel reinforcing wires, which provided a binding matrix in three dimensions. The material was used locally in the manufacture of solid fuel stoves, substitute steel girders for building construction, window boxes, pipes, slabs and so on. It was never developed on a large scale commercially due to lack of funds and facilities. In another case he developed an electric blow lamp, when he was consultant to the Yorkshire Copper Works in Leeds during the 1950s. This blow lamp was originally required for annealing, smelting and other applications in their works, where the use of paraffin, petrol or butane fuels would be dangerous. The idea was taken up later by other firms and similar lamps are now in common use in industry, workshops and households.

For his contributions to engineering science and practice George had been elected an Honorary Fellow of the Society of Engineers in August 1949 and in October of the same year he won the President's Gold Medal for his paper ''Scientists versus Engineers". In May 1954 he was awarded the Simms' Gold Medal for his paper ''A Hundred Years of Development in Mechanical Engineering" on the occasion of the Society's Centenary celebrations. He delivered his lecture on ''Sonics" before the Society in April 1959 for which he again received the President's Gold Medal.

After the end of World War II George was able to renew contacts with his old friends and colleagues in Romania and received many invitations to visit the land of his birth as an honoured guest. In 1956 he was invited to a reunion of all his colleagues who had attended Craiova High School with him, but he was unable to join them because of ill health. He was then seventy-five and had just suffered a coronary thrombosis as well as double pleurisy, which put him out of commission for more than a year. It was due to the prompt action of his doctor and Eva's constant care and nursing that he made a complete recovery. He had been an Honorary Fellow of the Romanian Academy of Science since 1920, and in 1961, although eighty years of age, he visited Romania accompanied by Eva, to receive the title of Doctor Honoris Causa in engineering sciences from the Bucharest Polytechnic Institute, the successor to the old National School for Bridges and Roads, at which he graduated in 1904. In 1963 he travelled to Romania again with Eva on holiday and rested at Constantza, before being honoured and feted in Bucharest on his eighty-third birthday. He returned to England in February 1964.

By this time George's body had become frail and weary from travel and excitement, although his mind was as sharp as ever. He continued to work on new ideas and mathematical analyses of problems, but just after his eighty-fourth birthday he had a fall from which he never recovered. He died at Oxen House on 12th December 1965, and was buried in the churchyard in the village of Lowick, just south of Lake Coniston in view of Coniston Old Man, the friendly mountain which had been the backdrop to his home for more than thirty-five years. The funeral was widely reported in the national and local press and on television.