No.
I think in central London, at HARRODS, there’s enough people of good standing you would seek to get support for a lost child.
Maybe, MAYBE, in a residential area at a quiet time, if you found a child without an adult you could possibly take them inside your home to phone police.
But in central London? TWO HOURS without speaking to police?
I might have some doubt whether he sexually assaulted her, but he fucking kidnapped her. No question about it in my mind whatsoever.