To put your minds at rest, it is a front door from a 6-wheel Gloster Saro or HCB-Angus converted TACR2, or a 6-wheel Gloster Saro RIV. They were converted from a normal 2-door Range Rover.
Even rarer are the rear doors, which were built from scratch.
For more information got to www.rr-conv.info/GlosterSaro/GlosterSaro.html or www.rr-conv.info/HCBAngus/HCBAngus.html or for more general information, try this www.rr-conv.info/FireRescue/TFFACR2.html, although some of the photos seemed to have got lost(?).
Clive