Cheers for that John, the fridge was huge but used to smell a bit!
That's the usual way to isolate a final drive, after the pub has been turned on the casing the reverser must be operated several times for the pin to locate the sliding dog in the center position. If the engines can't be run to create air pressure it can be supplied from a loco or another unit using the main reservoir pipe, obviously with the white circle system this can't be done