The royal couple rode the system's newest style train, the S-Stock, on its first line, which began running trains from Farringdon to Paddington Station on Jan. 9, 1863, The Guardian reported. Camilla, duchess of Cornwall, described the S-Stock cars as "very smart."
After swiping fare cards, the prince and duchess boarded an empty train at Farringdon and the public was then allowed to join them for the ride to King's Cross, although separated from them by a police contingent.
"Just one stop," Charles said when they exited at King's Cross.
The prince last rode the Underground 27 years ago when he opened Terminal 4 at Heathrow International Airport.
The couple toured King's Cross Station, now best-known at least outside Britain as the starting point of the Hogwart's Express, and visited the St. Pancras Renaissance Hotel. They traveled the 200 yards from the station to the hotel in more typical royal style -- a chauffeured limo.