The MOT due date snuck up on me again, and I figured the rear disc was a bit too far gone so stuck the spare wheel on.
I found the rear caliper had not appreciated 17+ years of all weather use. The pistons were almost solid in there, the brake lever moved them slightly, but I couldn't rotate them with the extraction tool. Didn't have time to pop them out and clean them properly so, with great difficulty managed to push them back in enough to suit the new disc, breaking a G-clamp in the process.
How, I don't know, but the brake worked and didn't even drag.
The MOT tester didn't like the slightly grooved disc (glad he didn't see the bad one!), but otherwise was happy… though took some convincing that the odometer was working correctly.