No Way Out (Originally Transmitted Christmas Eve 1975)
Fletch fakes pain from an old knee injury to wangle Christmas in the prison hospital. The Doctor is not going to allow him into the hospital unless he has a full check up and x-ray at the local civilian hospital. Fletch is then enlisted to assist in smuggling a blank passport to aid the never seen Tommy Slocombe's escape. In one of Porridge's classic scenes Fletch tries to drop Mackay in it but in the process wins himself the stay in hospital he was looking for all along.
Clip from "No Way Out"