Dual control T.4 WJ865 spent her whole flying career with the Empire Test Pilots School (ETPS) and the Aircraft & Armament Experimental Establishment (A&AEE) and was based at both Boscombe Down and Farnborough.
The left hand side of the T.4 cockpit was, essentially, a B.2 and to make it a trainer a second set of controls was added along with another seat for the instructor on the right hand.