The girl, believed to be 10 or 11, was seen wiping down tables and emptying bins at 10.30pm at the Foxtons’ Hampstead branch, north London, where homes sell for millions of pounds.

Marcus Butler, 38, had been walking past the office in Heath Street with his friends when he spotted the lone figure in the office.

He and his group stopped to watch for a few minutes, expecting to at least see an adult was supervising, but the young girl was seemingly working