Bartom
At the time of the loss of the Valiant at Wittering in 1960 I was training - as copilot - at 231 OCU Gaydon and our crew [Capt. Flt Lt Dave Brooke] were posted to No 7 Sqn to replace Flt Lt Wickham's crew on 5Dec60.
As I recall from 'crewroom discussion' or maybe flight safety 'feedback' the following may [or may not] be a reasonable explanation for the loss of the aircraft and crew:
The aircraft was fully fuelled for a training sortie - heavy, but 7Sqn aircraft did not carry underwing tanks at Wittering - and the 9000ft runway was fine for the purpose.
The aircraft took off / the nose wheel failed to retract - or the 'three greens' were two greens and a red.
Captain hands control to Co. and intstructs him to turn 'Downwind' whilst he starts the process of resolving this minor problem.
Co - whilst turning aircraft, listening to radio messages intercomm and forgetting [perhaps] the stalling characteristics of a heavy aircraft in a turn could, in theory, be at fault but - at the time this lesson was not highlighted at Flying Training or OCU's.
The lesson I learnt from this unfortunate accident was to be cool, calm and "follow the book" when an 'after take off' occurs. It stood me in good stead in 37 yrs of operational flying.