The spar failure was WP217 that happened at Gaydon in August 1964. They heard a worrying thump on the climbout and the OCU crew decided to bring it back. When they starting lowering flap the aircraft started to roll. They realised that only one flap was going down so they retracted it and landed it flapless.
The flaps on a Valiant had a single drive motor in the fuselage but, luckily, independent flap indicators. The spar had separated sufficiently for the flap drive to disconnect which led to the single flap failure.
The Valiant that did the wheels up at Manston was eventually a manufacturing error. They had a failure to lower on the starboard undercarriage and eventually they had to retract the gear fully and do a wheels up on the foam strip at Manston.
The aircraft was on a display tour and at one stage the starboard undercarriage had closed outside the door. I saw it at this stage and I was subsequently invited to the B of I.
The Valiant had three lowering systems; A main electric screw jack on the legs and doors, a secondary piggy-backed screwjack and a system that blew the doors and uplocks explosively and then used the main motors to lower the leg. The crew went through the checklist and came to the point where they would have to blow the door. There were two switches by the co-pilot; one for the port and one for the starboard. The co-pilot selected the appropriate switch but unfortunately, unknown to anybody, the switches had been cross wired at manufacture. Apparently having no effect on the faulty undercarriage the decision was then made to belly land it.