Aircraft design had come to the point that is was possible to be reasonably accurate when calculating the performance of an aircraft design whilst still on the drawing board. This was due to considerations such as wind-tunnel tests, scale models and previous experience. Having said this, these factors could not always predict to outcome, and one case of this occurred towards the end of 1937, when the Miles organisation built a machine to Air Ministry Specification No. T.1/37. This called for an elementary two-seat trainer, somewhat larger and heavier than the Magister and Hawk types, and powered with the 200 hp Gipsy Six engine.
Calculations and model experiments suggested that the specified performance of T.1/37 could not be obtained within the limits set by the Specification, nevertheless, a full-size prototype was constructed and tested - only to prove the slide-rule master of the situation.
In an effort to explore every possibility offered by the Specification a second prototype was designed and constructed, but little improvement in performance resulted. The final vindication of modern aircraft design investigation came in 1938, when the various machines built to the T.1/37 formula were subjected to searching official tests - none of them came up to the standards demanded by the Service and the type did not go into production.