They could call it Harry Potter and the Mystery of the American Housekeeper. The Home Office is probing whether actress Emma Watson’s maid has been working illegally at the star’s £2m north London home.

Officials are looking into claims that the housekeeper only had a tourist visa, which would bar her as a foreigner from working here. The woman was stopped by UK immigration staff who questioned how she could pay for her stay here, it was claimed.

Employers who breach the rules by hiring foreign staff illegally can face a fine of up to £10,000. Watson, 24, who played Hermione Granger in the Harry Potter films, first started using the maid’s services in her New York apartment last year.

But the woman allegedly made trips to London and was paid to help out at the star’s three-storey Georgian terraced house in Islington, it was claimed.

Between September last year and February this year, she is said to have spent a total of three months in the UK. It was on one of her trips to London that UK Border Agency staff allegedly questioned her about her ability to pay for her stay.