On the British taxpayers dime.
This could get interesting. If you’re a slimebag billionaire like Epstein and you’re hosting the rich and powerful on your island for sex with underage hookers you’d be crazy not to have cameras hidden to record everything for blackmail purposes if you needed it. There’s no telling who might pop up during the course of the investigation, that is if the public was ever allowed to find out, which is doubtful.