Thanks Rosie,
I had looked for him on the 1939 Register on Ancestry and not found him. They're completely mistranscribed, for example as "Patrick Gabrielle U R J Fitz" for his mother (in the image the surname is obviously one word as Fitzpatrick, the U and the J are the tails of letters in the redacted line above).
I think I know the link now, I have a Gabrielle Rosalie Gilles (her mother's maiden name was Heulard), who was a sister of my father-in-law's great grandfather. I have her date of birth as 28 Jul 1890, but this could be mistranscribed from elsewhere.
James