Failed MOT - Offside Rear Parking Brake "Inoperative"

[Carolyn]

Looks like the old caliper had a partially seized piston - the new one travels a lot more. Lubed the cables as well and it has passed the MOT. Got a spanner trapped between the dashboard and the windscreen in the process...

Well done!!  Result.  That spanner should be fun.  

[Ardent]

Got a spanner trapped between the dashboard and the windscreen in the process...

That is some going. 
I pray thermal movement does not have a joker to play.

[Joesson]

Looks like the old caliper had a partially seized piston - the new one travels a lot more. Lubed the cables as well and it has passed the MOT. Got a spanner trapped between the dashboard and the windscreen in the process...

The pistons can get very tight in the caliper, regular movement/ use likely "eases" that situation.
Maybe a magnetic telescopic type recovery tool will help retrieve the spanner.