The Valiant losses were not due to an operational change from their original requirement but through metallurgy and the premature failure of the advanced alloys in the spars, spars never installed were found to exhibit the same stress signs. Aircraft assigned to RRE were very low hours and similarly afflicted.
The RAF knew in at least 1956 that there was a problem with DTD 683, the alloy the Valiant centre plane spar was made out of, but the materials low fatigue resistance was known from the very begining of the Valiant project in 1947, it was hoped that new techniques in manufacture would solve this inherent weakness. The other problem for the Valiant was that it was built to a 'safe-life' strategy, the 'safe-life' strategy of A/c design was abandoned in around 1956 as it could not ensure safety in a catestrophic failure. Also in 1956 this article:-
1790 Structural Changes Caused by Plastic Strain and by fatigue in Aluminium-Zinc-Magnesium-Copper Alloys Corresponding to DTD.683 (Broom and Mezza)
appeared in
The Journal of the Institute of Metals (JIM) Vol 86, 1957-1958, (written in November 1956)
The President of the Institute of Metals was Lord Tedder, Marshal of the RAF .
Lord Tedder