I agree that in RAF service the minimum crew was 4, 2 pilots, AEO and a Nav. However at Boscombe in 1982 I flew the tanker conversion with just 3 crew, 2 pilots and myself as AEO on high risk trials (heavyweight rollers at 205K AUW to determine how quickly the aircraft slowed, as we couldn’t aerodynamic brake due to the HDU on the back). We also delivered XH558 to Waddo at the end of the trials with a 3 man crew, just because we didn’t have a Nav available - under A&AEE rules!! After she was restored we flew XH558 with a 3 man crew, 2 pilots and an AEO, as the CAA insisted minimum crew for air displays, and we didn’t need a Nav as XH558 had GPS fitted when she was restored. We did occasionally fly with a Nav on transit sorties which didn’t include a public display! Happy days 😊