LONDON - Royalty means rarely having to mind the gap.

Britain's Prince Charles took a ride on the London subway Wednesday — for the first time in a quarter century.

Charles and his wife, Camilla, joined transit officials and commuters to mark the 150th anniversary of the Underground, the world's first subway system.

The subway system, which sees 3.5 million journeys a day, is well known for announcements warning passengers to "mind the gap between the train and the platform."

The royal couple traveled one stop, from Farringdon to King's Cross on the Metropolitan Line — the oldest section of the subway system, opened in 1863.

Charles last traveled by subway in 1986, when he and the late Princess Diana took the Tube to Heathrow Airport to open a new terminal.