Star and Vauxhall cars and Overtime Tractors. Ferguson saw at first hand the weakness of having tractor and plough as separate articulated units, and in 1917 he devised a plough that could be rigidly attached to a Model T Ford car—the Eros, which became a limited success, competing with the Model F Fordson. In 1917 Ferguson met Charles E. Sorensen while Sorensen was in England scouting production sites for the Fordson tractor. They discussed methods of hitching the implement to the tractor to make them a unit (as opposed to towing the implement like a trailer). In 1920 and 1921 Ferguson demonstrated early versions of his three-point linkage on Fordsons at Cork and at Dearborn. Ferguson and Henry Ford discussed putting the Ferguson system of hitch and implements onto Fordson tractors at the factory, but no deal was struck. At the time the hitch was mechanical. Ferguson and his team of longtime colleagues, including Willie Sands and Archie Greer, soon developed a hydraulic version, which was patented in 1926. After one or two false starts, Ferguson eventually founded the Ferguson-Sherman Inc., with Eber and George Sherman. The new enterprise manufactured the Ferguson plough incorporating the patented "Duplex" hitch system mainly intended for the Fordson "F" tractor. Following several more years of development, Ferguson's new hydraulic version of the three-point linkage was first seen on his prototype "Ferguson Black" or ‘Irish tractor’ as Harry called it, now in the Science Museum, Kensington, London. A production version of the "Black" was introduced in May 1936, made at one of the David Brown factories in Huddersfield, Yorkshire, and designated Ferguson Model A tractor. Ferguson's interests were merged with those of David Brown junior to create the Ferguson-Brown Company. In October 1938, Ferguson demonstrated his latest tractor to Henry Ford at Dearborn, and they made the famous "handshake agreement". Ferguson took with him his latest patents covering future improvements to the Ferguson tractor and it is these that led to the Ford-Ferguson 9N introduced to the world on 29 June 1939. The 1938 agreement intended that the Ferguson tractor should also be made in the UK at the Ford Ltd factory at Dagenham, Essex but Ford did not have full control at Dagenham and, while Ford Ltd did import US-made 9N/2Ns, Dagenham did not make any. Henry Ford II, Ford's grandson, ended the handshake agreement on 30 June 1947, following unsuccessful negotiations with Ferguson,