You'll never guess who I had in the back of my cab

His father is said to have one for his personal use. But for Prince Charles today it was his first trip in a London black cab.

While Prince Philip uses his Metrocab to get around the capital privately, Charles's journey was part of a tribute to the city's black cab drivers.

A source said: "Black cabbies provide an iconic part of London's identity."

And referring to the exhaustive learning process it takes to become a fully-fledged cabbie, the source added: "The Prince is full of admiration for their passing the Knowledge."

Charles was driven by John Sheen who said afterwards: "You know what I'm going to say...'Guess who I had in the back of my cab today'."

Mr Sheen, a driver for 30 years, added: "I don't think they'll believe me. He's never been in the back of a cab before. He said as a boy he went on a double-decker bus but that's about it."

Charles was picked up at Kensington Palace and driven to a traditional green wooden taxi drivers' shelter in Hanover Square.

There he joined cabbies for a mug of tea - although he was given a somewhat delicate cup decorated with flowers.

Mr Sheen, 65, from Newbury Park, Essex, said Charles paid his own £9.20 fare. "He got out of the cab, took a tenner out and said, 'How much was that?'" Asked if he had received a tip, Mr Sheen added: "He said, 'I should give you that' and I told him not to worry about it."

Afterwards, at a reception at Clarence House, Charles described how cabbies played a significant part in the community "providing a reliable service, helping make London safer and assisting the police in combating and deterring crime". He said they also did a lot for charity and boosted tourism. The reception was for more than 100 drivers and was part of Charles's campaign to celebrate unsung heroes.

Also at the function were representatives from the leading trade associations, charities and the main school teaching the Knowledge.

Princess Diana regularly used black cabs for private appointments, sometimes with William and Harry, and had her own account.