The Borgified Corpse wrote:
ISTR that in Terrance Dicks's script Benton was supposed to be the sergeant who has to identify the Doctor for Crichton at the end of the scene (continuity mangling though that would have been).
Well, that really only would have mangled to continuity of "Mawdryn Undead," which has so severely mangled the continuity of nearly everything else it touches (and is rubbish to boot).
Plus, there is a fan theory (based largely on Nick Courtney sporting a full head of hair in Five Doctors, thanks to a toupee, whereas he had a bald patch in the 'late' bits of Mawdryn) that the Brig in the Five Doctors was at his retirement party, in between season 13 and the 'early' bits of Mawdryn.
IIRC, John Levene was asked to do that scene, but didn't want to do a one-line cameo (there's a few other characters in Terrance's script who were supposed to be established characters in minor roles, but mainly Time Lords from Arc of Infinity, including Commander Maxil - Terrance having written the book version of Arc just as he was commissioned for 5Docs. In the event, the Castellan was the only actor who returned).