Pyramids of Mars, thanks to Watch. This was more like the DW I remember from my childhood. Also featured Michael Sheard, Grange Hill's Mr Bronson and Empire Strikes Back's Admiral Ozzel and who would return to DW for Remembrance of the Daleks.
The main star, of course, was Tom Baker, who was as watchably bonkers as ever and ably supported by Liz Sladen as Sarah Jane. Quite a good story, even with its creaky SFX and make up but boosted by the chemistry of its leads and Baker's loony charisma.