That's gotta be either custom or fake. I don't think we're past "D"
F plates were issued starting in 2019 as the French slogan plates (TANT À DÉCOUVRIR) instead of the English (YOURS TO DISCOVER). Previously there were special series of normal plates with that phrase (BEAA, BSRJ, BTBF, and others).
I love stuff like this on plates, also a plate snob too. Huge ick when the plate doesn't match the production era of the car, like a 2011 G37 with a D plate.
I had a client with a plate "MAC XXX" that's issued to medical doctors, so anything with a MAC is a Doctor, the more you know.