Back on thread (I think).
I met an ex-Shack Mk3 AEOp, then a Vulcan AEO, who was one of the crews at a Farnborough air show that demonstrated the capability of the aircraft to fly for 24 hours.
On the first day a Mk 3 departed. On the second day another departed and the first returned having been airborne for 24 hours.
It had simply flown up and down the Channel at endurance speed. As he wryly observed, they could have flown to St Mawgan, had a few beers, been instructed not to shave, and flown back the next day, but they did fly for 24 hours.
This was in the mid-50s I believe.