The specialist hospital for burned pilots is based on the Queen Victoria Hospital in East Grinstead which specialised in experimental reconstructive plastic surgery during the war. The social club and mutual support network of the burned pilots was called the Guinea Pig Club.
Matron calls the stolen drug diamorphine hydrochloride. This is a form of morphine that is used primarily for pain relief, as well as water retention in the lungs, and for treating heart attacks.
Andrew is promoted to Flight Lieutenant. This is two steps up from where he began, with the two lower ranks being Pilot Officer and Flying Officer. It is also one step below Squadron Leader.
As can be determined by the tombstone, Foyle's wife Rosalind died in 1932 at the age of 29. As Andrew is 18 in 1940, he would have been born in 1922, which means that his mother was eighteen when she married, which would have been in 1921.
The headstone on Foyle's wife's grave which he visits on the ninth anniversary of her death reads: "Rosalind Foyle / June 1902 - February 1932 / RIP".