Test running log for Whittle W.1 engine, prefaced by note 'Whittle Supercharger W1. Manufactured by B.T.-H. Co. Ltd Rugby & modified & re-assembled by Power Jets, Ltd at Ladywood Works, Lutterworth'. Covers period 12 April to 30 May 1941 with details of several tests per day. Each left-hand page bears details of modifications and repairs; each right-hand page includes details regarding the duration of the test and reasons for stopping, remarks, faults and defects found on inspection and total running time. The first flight, in a tricycle gear Gloster E.28/39, was on 15 May 1941; on 21 May 1941 there was a demonstration flight for the Secretary of State for Air et al.