I just came upon another undefined abbreviation in Bill Kirkness' raw manuscript: FFI.

The troopship transporting him from Cape Town to Liverpool had just docked, and all the RAF airmen aboard were transported to Wilmslow. Here is the context of Bill's use of "FFI":

Travelling to Wilmslow was enjoyable. The day was warm and sunny. England in July 1942, even in wartime, was infinitely better than many places on the Earth. Entering the camp gates eventually, the occupants of the three-tonner were in the best of spirits, looking forward to leave and reunions with families and girlfriends. The RAF did its best to curb this exuberance, in the shape of a Flight Sergeant (Discip.) who stood to the rear of the waggon as the good-humoured aircrew “debussed” – a word only the military mind could have conceived.

“Shut up you, and listen. You will be marched to Stores and kitted out. Go to sick quarters for jabs and an FFI. From there make your way to Accounts for pay and finally to the Orderly Room for leave passes.” The flight sergeant regarded them with disgust, not without reason, for all were in varying stages of dishevelment. Looking straight at Bill in his khaki shirt and trousers, topped off with his blue battle dress blouse, he wrinkled his nose and snorted, “My God, you look like a turd in tapes.” The stripes on their arms were always referred to as tapes.

Can anyone offer me an explanation for "FFI"? It has something to do with medical requirements.