Bored in lockdown ,I've been looking at adding a double USB socket in a better position than where the ciggie lighter socket is, and also ( for when things get back to normal,and we grandson sit, a USB socket nearer the rear ). So I've been looking at the fusebox for suitable fuses to piggyback using fuses on the x contact. Then I found ----

Fuse 10 on the Haynes manual. An on my fusebox  there is a 5A fuse fitted. From looking at the wiring diags I know that the "x" contact  supplies power to those circuits that are only powered when ignition is on. But looking at the other wiring diagrams i cannot see any mention of anything supplied from F10. Any ideas on F10 and "s" contact ?

Looking at the diagrams on Elsawin the "S" contact comes out of the ignition switch through to F10 then to the Onboard power supply unit and the radio 

Thanks, Nige- .Looks like it's something else Haynes thinks we don't need to know about .