Expat's children working laws? (London)

Hi,

We moved from Belgium to London in March Protected content . My husband is working as IT consultant and I don't work anymore.

We have a son of 19 y old now who stayed at school in Belgium to finish his last year in a secondary school before to join us here and go to one of the London's university as we planned.
But he failed and now he wants to work. Does he need a permit to work if he's living with us?
What is the procedure?
Thanks for your answers.