On the 6th of August 1964, the crew of WP217 of 232 OCU felt what appeared to be a large impact when flying a training mission. With multiple warnings indicated, the crew elected to try and land their stricken aircraft. Incredibly, with the starboard wing's rear spar seriously fractured (so much so that the wing was noticeably sagging), a successful landing was made. The RAF and Vickers had already begun inspecting Valiant spars before this incident, after Vickers had found fractures in Viscount spars (made from the same alloy). After the WP217 incident an emergency spar inspection programme was put into place and the enormity of the problem was soon apparent - the majority of Valiants had significant stress fractures. Low level operations ceased immediately and other operations were seriously restricted while the cost of repairing or replacing the fatigued spars was looked into. With two other V-Force bomber types performing well, the cost of refurbishing the Valiant fleet was simply too high, and the Valiant force was grounded completely in early December. The entire fleet was retired in short order, with the OCU being first to disband and the last Valiant squadron, 49 Squadron, being disbanded in January 1965.
The RAF was suddenly without its tanker force and Victors were hurriedly pressed into service in this role to replace the lost Valiants. Of the Valiants, most were scrapped at their bases very quickly after the disbanding of their operating squadrons. Others became fire training airframes, being burnt quickly, or 'damage to aircraft' targets. Several remained in flying condition, being on loan to what was now the British Aircraft Corporation (incorporating Vickers) for various flight test purposes. A single example was earmarked for preservation, and was appropriately enough XD818 - the Valiant that dropped the UK's first hydrogen bomb. Once BAC had finished with their four Valiants, they were stored for a while and then finally scrapped, though not before one of them, XD816, had taken part in the flypast on the 29th of April 1968 to mark the disbandment of RAF Bomber Command (which was now becoming Strike Command). The final remaining Valiant, XD818, stood guard at RAF Marham for many years before being moved to the RAF Museum at Hendon. More recently it has been moved once again, to its permanent home in the National Cold War Exhibition at the RAF Museum at Cosford.