They're not exactly regular tube users, so commuters were rather surprised to see Prince Charles and The Duchess of Cornwall underground this morning. The Royal couple swiped in using their own oyster cards, like the rest of us, but their journey was anything but average, as Rags Martel reports.
Today's journey was the first ever joint tube trip for Prince Charles and the Duchess of Cornwall.
Although both of them now qualify for an over-60s Freedom Pass, they were presented with commemorative Oyster cards topped up with £10 credit for the one stop journey from Farringdon to King's Cross.
A brand new train was used, which arrived at the platform empty. But members of the public boarded along with the royal couple - separated only by a group of policemen standing further down the carriage.
When the royal couple arrived at King's Cross they were taken to "Platform nine and three quarters", a Harry-Potter themed attraction in the station.
In the books by JK Rowling, the "Hogwarts Express" steam train leaves from a secret platform, which witches and wizards reach by pushing a trolley through a wall.
But Charles and Camilla remained firmly in the land of the "muggles" or non-wizards.
After the royal couple's trip on the Metropolitan Line, Clarence House tweeted this picture of the Duchess of Cornwall at "Platform 9 3/4" at King's Cross station.
Clarence House has tweeted pictures of Prince Charles using an Oyster card to pass through the ticket gates at Farringdon Station.
The Prince of Wales and the Duchess of Cornwall are visiting the station to mark the 150th birthday of the tube.
The royal couple were presented with special commemorative Oyster cards.
The age of steam returned to the London Underground today, to mark the 150th anniversary of the first ever tube journey. Hundreds of rail enthusiasts and families lined bridges and stations between Kensington and Moorgate to catch a glimpse.
Among the lucky passengers was Mayor of London Boris Johnson and our reporter Ria Chatterjee.
Boris Johnson was one of the passengers on a 19th century tube train which travelled through London today to mark the 150th anniversary of the underground.
He said there was something "very romantic" about imagining all those Victorians in the carriages.
A 19th Century steam train took passengers on the London Underground today to mark the 150th anniversary of the first Tube journey in the capital.
Specially invited passengers moved off from Kensington Olympia Tube station in west London aboard a train pulled by Met Locomotive 1, which was built in 1898.
It was the train line they said would never work - but this week the Tube is celebrating 150 years of service.
It was in 1863 that a steam train travelled five miles on the first line - and the UNderground was born. And last night that journey on the Metropolitan line was recreated