Sebastien, is looking for a part time nanny in London W1H

Hello, I need someone to spend time with me when I see my son after school from 3.20pm to 6pm every Thursday and every other Friday.
On Thursdays, Romeo needs to go back to his mother and on Fridays he stays with me for the night.
I live in Swiss cottage and his mother lives in Maida Vale. Romeo goes to school at King Solomon academy.
I will be taking care of him but occasionally, I may need help with him during a work call.

I’m 40, from France, I work at the EBRD, I live with my partner who may be here as well and Romeo is my 3rd child. My 2 daughter (13 and 14), live with me 5 days every 2 weeks and half their holidays.

I’m looking for someone as discreet as possible. I want Romeo to be fully aware that I, and not the babysitter, is watching and playing with him.
If anything, I would appreciate help with cooking and or tidying up bit that should be minimal.