After the
Armistice with Germany, now a
major, Martel was able to combine his two interests of tanks and military bridging when he became head of the
Experimental Bridging Establishment at
Christchurch, Hampshire, which researched the possibilities of using tanks for battlefield engineering purposes such as bridge-laying and
mine-clearing. Here he continued trials on modified
Mark V tanks. The bridging component involved an assault bridge, designed by Major
Charles Inglis RE, the Canal Lock Bridge, which had sufficient length to span a
canal lock. Martel, who attended the
Staff College, Camberley, from 1921 to 1922, also developed his new bridging concept at the EBE, the Martel bridge, a
modular box girder bridge suitable for military use. The Martel bridge was adopted by the British Army in 1925 as the "Large Box Girder Bridge". A smaller version, the Small Box Girder Bridge, was also formally adopted by the Army in 1932 and copied by many countries, including Germany, who called their version the ( for short). Martel also continued to pursue his interest in tanks independently. In 1925 he built, in his own garage, a one-man
tankette powered by a car engine and capable of a speed of . After a demonstration to the
War Office,
Morris Commercial Cars was contracted to build four test models, the first of which was delivered in 1926. Carden Loyd Tractors built a similar one-man machine, the
Carden Loyd One Man Tankette. In 1927, eight more Martel tankettes were ordered to assess their potential role in forward reconnaissance. They were tested along with two-man
Carden Loyd tankettes in manoeuvres with the
Experimental Mechanized Force on
Salisbury Plain in 1927 and 1928. The idea for a single-man fighting vehicle was soon dropped as it became apparent that one operator could not control the vehicle at the same time as firing a weapon and the British Army requirement for a light tank, the
Light Tank Mark I, was a development of the Carden Loyd tankette. Morris Motors tried developing a two-man version of the Martel design and
Crossley Motors a further version – the
Morris-Martel – in 1927 with
Kégresse rubber tracks but after two prototypes were tested the project was abandoned. In 1928, the Tank and Tracked Transport Advisory Committee that Martel was a member of became the Mechanical Warfare Board which was to liaise with industry and to advise on technical matters relating to "mechanised transport". In 1929, Martel was seconded to the
King George V's Own Bengal Sappers and Miners and then served as an instructor at the
British Indian Army's
Staff College in
Quetta from 1930 until 1934, after which he attended the
Imperial Defence College. 1931 a invention by Martel concerned a vehicle drive system, and in particular the patent GB386987, which described an invention for a combined wheel-cum-track-drive system. From 1936 until 1939, Martel served at the War Office, first as Assistant Director of Mechanisation, then from 1938 as the Deputy Director with the temporary rank of Brigadier. In 1936, he attended along with Wavell a large-scale tank exercise in the Belorussian Military District of the
Soviet Union in which large numbers of the Soviet
BT tanks took part. Martel pressured for a similar fast tank design to be investigated for addition to British tank brigades and convinced the General Staff to issue a specification for a cruiser tank. Martel was appointed
General Officer Commanding the
50th Northumbrian Division, Territorial Army in February 1939 with the rank of
major-general. The division had been converted from October 1938 to "motorised" with the whole of the infantry being carried by large lorries. ==Second World War==