The RAF Museum Hendon have crash report cards giving the basic details. Here's one for Valiant XD864, August 1960:
The text reads:
The nosewheel failed to retract following a normal take off. The P was informed by ATC and acknowledged this by saying staying local to 'sort it out'. No further communication was received. A was seen by witnesses soon after levelling off to turn port and after this turn it 'wobbled' and 'appeared unsteady' and then descended rapidly. The port wing dropped but wings were levelled after this and A went into a shallow dive. From this descent A dropped the port wing and struck the ground. Shortly before impact, a sudden increase in E power was heard. On impact the A exploded, caught fire, and all the occupants were killed.
Board found primary cause of accident was that P in control (assumed Co P) entered the turn with insufficient speed and/or E power to maintain an adequate safety margin over stalling speed for the relevant flight configuration i.e. clean A. Contributary causes were (a) The failure of the nosewheel to retract. (b) P error in retracting flaps before complete retraction of U/C contrary to procedure as laid in Valiant pilots notes. There was evidence to show that the preparation for the flight was hurried. A.O.C-in-C states this accident has revealed an unsatisfactory state of affairs in No 7 SQDN.