The Magister trainer had been built in many hundreds by 1938, but Mr Miles felt that he could produce an even better machine within similar specification limits, and proved his theories with the Trainer M.18, which flew for the first time in 1939. Beyond the fact that it was a tandem two-seat low-wing monoplane, the M.18 had nothing in common with the Magister.
The main design considerations were ease of handling and serviceability, and these aims were attained in a high degree, the machine being most delightful to fly, with controls light and positive right down to the stall.
In the course of extended trials several variants of the M.18 were tested, with open and enclosed cockpits, tail-wheel and tricycle undercarriages, and with the Gipsy Major and Cirrus Major engines, the combined results proving that the machine was an ideal training type.
After successful official acceptance trials the M.18 was ordered for quantity production, but the order was almost immediately reversed because the existing biplane design was in large-scale manufacture. Then, in 1942, the machine was again ordered for production, but official policy was again changed and the M.18 was cancelled once more.