I now have the truth.
The decision to re-locate all the aircraft in the british airways collection was made by british airways following a review of their condition and the support provided for their maintenance. The Trustees of the Royal Air Force Museum were no longer able to provide space for these aircraft without proper support being provided by ba and covered accommodation was becoming urgent to ensure their long term preservation. A joint review was carried out between ba and the RAF Museum and the decision to re-locate the aircraft was made by ba.
ba have already started the work of destroying the Trident 1C, I am informed, and only the cockpit section will be going to East Fortune. The VC10 is still intact, but only the cockpit and front fuselage section will be going to Brooklands.