Here we are, more on XH536, and TFR trials are mentioned.
http://www.clwb-cerdded-ystalyfera.i...ages/xh536.htm
Vulcan Bomber XH536 of R.A.F. Cottesmore
11th February 1966
SN 913215 Fan Bwlch Chwyth at about 590 m
Reason for Flight
TFR trials [ Terrain Following Radar]
Cause of Crash
A low flying exercise that went badly wrong when the weather conditions become too bad for safe aircraft operations in the low level role, and the Pilot did not elect to fly at a higher altitude.
And more;
http://www.gpswalker.cwc.net/volcan.htm