The appearance of two familiar figures ignited a short-lived frenzy among journalists perched outside the Lindo Wing of St Mary's Hospital.
The regal looking pair stepped out of a blacked-out land rover and made their way to the top of the entrance of the private hospital, but the police officer at the door spotted they were not the Duke and Duchess and accompanied them back down the stairs.
The lookalikes were part of a stunt by tabloid newspaper, The Sun.
Bookmakers Paddy Power have cut the odds on the royal baby being born in August from 60/1 to 33/1.
A royal fan, who is camped outside St Mary's Hospital ahead of the birth of the Duke and Duchess of Cambridge's baby, said he would wait "however long it takes".
John Loughrey said he was "exploding inside" with excitement about the birth of the royal baby.
The Sun's royal photographer Arthur Edwards said the media frenzy outside St Mary's Hospital ahead of the birth of the Duke and Duchess of Cambridge's baby was "phenomenal" and very different to when Princess Diana was pregnant.
One of the biggest fans of the royals has begun his tenth day waiting outside St Mary's Hospital for the birth of the Duke and Duchess of Cambridge's baby.