The Queen, dressed in a pink jacket and wearing pearl jewellery, sat in a black cab that drove past the spectators camped outside the hospital.
Except it was not Queen Elizabeth II but a very lifelike wax statue of the British monarch.
It's not clear whose idea it was to prank the audience outside St. Mary's Hospital, but we have to admit, it was a good one.
According to several journalists present outside the Lindo Wing, the statue of the monarch caused quite a flurry outside. The wax mannequin became hot topic on social media.
The first royal appearance for the new #RoyalBaby ... of sorts. 'The Queen' in a London black cab. #BabyCambridgepic.twitter.com/xvNA7Nusie
— James Brookes (@jamesbrookes_) April 23, 2018
LOL at the fake mannequin of the Queen driving by in a black cab outside the Lindo Wing #royalbaby#lindowingpic.twitter.com/x2wJ4MykZj
— The Blonde Tonic (@AmmeGrace) April 23, 2018
A scarily good waxwork driving past the Lindo Wing #royalbabywatchpic.twitter.com/qrZIDOB4WK
— Ben Jary (@BenJary) April 23, 2018
Flurry of excitement when the 'Queen' arrives #LindoWingpic.twitter.com/VVVyeP3ygj
— Kate Williams (@KateWilliamsme) April 23, 2018
On Monday, Prince William and Kate Middleton became third-time parents to a baby boy, who will be fifth in line to the British throne. Kensington Palace said the baby was born at 1001 GMT and weighs 8 lbs 7oz (3.9 kg). William was present for the birth at St Mary's Hospital in west London where their other two children, George and Charlotte, were also born, it added. Elder siblings Prince George and Prince Charlotte posed for cameras as they arrived at the hospital to meet their younger brother.
Albert, Arthur, and Fred are among the top favourite names with bookmakers for the royal baby boy.

Kate Middleton and Prince William with their newborn son outside St. Mary's Hospital (Reuters)