Last night I fired up Snowdrop and put her in gear. She was still the same (no drive) but when she was in gear I had a look underneath to see if the propshaft was turning. It wasn't so I've eliminated a broken half shaft in the axle. The problem is either a slipping clutch or a gearbox problem. I won't know until I remove the gearbox.
This morning the front passenger door wouldn't shut properly on Blue. I tried some penetrating fluid on the latch mechanism (made no difference) and then I loosened the striker plate, moved it out a bit and after it was tightened it cured the problem. Odd.