In the 1930s, a young woman by the name of Lily Margate went to an agency in Mayfair seeking a position in service. She soon secured a post as an under-housemaid at an elegant home in the area. 

On her first day, the officious head housemaid, in interviewing her, did not even bother to ask Lily her name. 

Her Ladyship always likes the under-housemaid to be called Mary, she declared. 

And from that point forward, Mary she became.