The meeting, on 5 June, was not an isolated contact between Prince Charles and the man dubbed by his enemies the Prince of Darkness. Prince Charles is intrigued by Mr Mandelson - as one royal insider put it: "If you had the terrible PR problems he does, you would admire someone who had those skills. You would be interested in meeting and learning about him."
But this growing friendship between the "two Princes" may be founded on more than Prince Charles's desire to learn from an acknowledged master of presentation and image manipulation. A tricky constitutional problem is looming, one they both share: Prince Charles in his personal capacity and Mr Mandelson as the eyes and ears of Tony Blair, and the Government's fixer of problems before they even arise.
Increasingly, reports in the media have said that senior figures in Whitehall are considering the implications of a marriage between the Prince of Wales and his mistress Camilla Parker Bowles. Equally, such stories have been dismissed as premature.
However, if it does become a possibility, government would inevitably be involved, at the very least because legislation would be required. In those circumstances, who better to smooth its path, to act as a link between Palace and Downing Street, than Mr Mandelson? As one source put it: "Matters to do with Camilla would have to be dealt with ultimately by Blair. But one might not want to go directly to Blair. One might try things out with Peter en route."
Intriguingly, Mr Mandelson and Mrs Parker-Bowles have met, over dinner, at a secret location - aides insist it was not at St James's Palace. Mr Mandelson would not have felt uncomfortable, since for a Labour politician he moves in a socially glamorous world. As well as Prince Charles, he also shares other friends with Mrs Parker Bowles, such as Lady Carla Powell, wife of Sir Charles Powell, Margaret Thatcher's former foreign adviser, and Lady Antonia Douro. Mr Mandelson knows several of the Prince's close aides well, including Tom Shebbeare, director of the Prince's Trust.
Wherever it was held, the dinner meeting between Mr Mandelson and Mrs Parker Bowles was a success. "It would not be unfair to say that they got on," was one source's verdict. Then there is the developing closeness between the Prince of Wales and the new Labour government. This week, for instance, Charles, known in some Cabinet circles as "Chazza", will meet four senior ministers.
What one source describes as a "love-in" between New Labour and the future monarch goes right to the top. The relationship between the Prince and Mr Blair is said, both by Government and Palace sources, to be "warm".
The two held a much-publicised meeting aboard the royal yacht Britannia in the harbour of Hong Kong on the day Britain handed the colony back to China. In fact, they had met earlier in the Blair prime ministership, after Prince Charles had presided at a Privy Council meeting (the one which accepted the resignation of Jonathan Aitken, the disgraced ex-Cabinet minister). After the Privy Council session, the Prince and Mr Blair repaired to a private room at St James's Palace, spending more than an hour-and- a-half together over lunch, alone.
The warmth of their relationship should not be surprising. The Prime Minister and the heir to the throne first met in June 1990 - an introduction brokered by Mr Mandelson. Then Labour's director of communications, credited with reviving the party's bruised image, had been invited to a reception at Kensington Palace.
The Prince greeted him with the words "Ah, the red rose man" as Mr Mandelson arrived at the receiving line and, as they chatted, asked to see some leading lights on the shadow front-bench, suggesting Mr Brown, Mr Blair and John Smith. That meeting was dominated by issues of employment and training - issues which still dominate the Prince's concerns.
Colin Byrne, managing director of Shandwick PR and a former aide both to Labour and Prince Charles, believes Labour has come round to the heir to the throne's thinking. "It is," argues Mr Byrne, "more a question of Labour sharing the view of the legitimate social role of business expounded by the Prince, rather than him crudely hitching his chariot to Labour."
Government and Palace aides play down the rapport. There have been only two, formally documented, meetings between Mr Mandelson and Prince Charles in seven years. Neither Mr Mandelson, nor any other senior minister, is, as one source put it, "a house-guest" of Prince Charles. And, when Mrs Parker Bowles has her 50th birthday party this week at Highgrove, the Prince's country home, the guest list will not include the MP for Hartlepool. As with Mr Blair, though, he is just a phone call away.Reuse content