XD674, the first of 9 development T.1s, spent most of her time with Hunting Percival and Armstrong Siddeley. Service trials of the T.1 began at the CFS, RAF Little Rissington in July 1955, and from August 1955 at 2FTS based at RAF Hullavington.
Built as pre-production Jet Provost it entered RAF service as XM129. After restoration it initially flew in factory colors as G-AOBU; later it was falsely marked 'XD693'.