All MI5 had to do was send a spook out from its headquarters and across Lambeth Bridge and the mystery of Charlie Chaplin's birthplace would have been cleared up.
It has always been thought that the star of The Great Dictator and The Gold Rush was born in Walworth, south London, on April 16 1889.
When the FBI - on the hunt for communists - asked MI5 for information about the actor's background the nation's finest couldn't find any record of his birth at Somerset House.
So, according to a newly released file by the National Archives, a report concluded: "It would seem that Chaplin was either not born in this country or that his name at birth was other than those mentioned."
There was even talk that he may have been born in France, but that also came to nothing.
But if MI5 had had a chat with the King family in the Elephant and Castle they would have told them the facts. They actually knew his folks.
Father of three John King told the Morning Star today that his paternal grandmother Mabel King knew the Chaplin family, but she was certainly not one of his fans.
Mr King, acting assistant manager at a local post office, said Ms King, who died in the mid-1980s, wasn't keen on him "because he didn't fight in the first world war, he changed his nationality and didn't pay what she thought was his due in taxes."
His mother Ethel told the Star: "My mother Alice Stone, who died in 1972, actually went to school with Charlie's brother Sid - they went to St Mary's School."
Great-grandmother Ms King, 82, said her mother recounted that they rarely talked about Charlie.
Mystery solved. Chaplin died at Vevey, Switzerland, in 1977.