Monaco was developing two flat-fours, a 3 3-litre and a 3.6-litre, producing, respectively, 75 hp and 100 hp at 2,200 rpm. A prototype bench ran, and was due to have been flight-tested in an Auster Autocrat, but I don't think this ever took place. The Monaco was to have been supplied as a firewall-forward ‘power egg’, complete with cowling. At the same time the Engine Branch of the Nuffield Organisation was developing a 3.82-litre, 100 hp flat-four that was to power the two-seat, magnesium-skinned Essex Aero Sprite. And Roy Fedden Ltd was developing direct-drive and geared flat-sixes of 160 hp and 185 hp respectively. They were low-profile engines (just 14 in high) and could have been ‘buried’ in wings of twins driving propellers via extension shafts. Erco, manufacturer of the Ercoupe, had a development contract with Fedden, but the loss of a Ministry of Supply contract to develop the Cotswold turbine engine, and Erco’s withdrawal from the flat-six project, led to the Cheltenham’s based company’s closure in the summer of 1947.