It was not their first meal together this year. At Easter, the Blairs went to stay at Pena's Spanish residence, an austerely beautiful, medieval, Moorish house, built around two galleried patios in the Juderia, or Jewish quarter of his home town of Cordoba. Their visit was not as long as had originally been planned - events in Northern Ireland and the Middle East saw to that. But it was notable enough to attract the attention of Fleet Street and to provoke excited claims that Paco was teaching Tony to play the guitar.
He had even, it was said, lent the PM his cherished Gerundio Fernandez - a guitarist's Stradivarius. It was a delicious image: the world's finest exponent of flamenco instructing our Caesar-cut premier in the cool darkness of some Spanish bodega, while Cherie - her hair raven-black, her lips cherry-red - stamped a haughty foot and rattled her castanets.
Paco Pena is a genius. His close friend and fellow guitarist, John Williams, has said he would give his eye-teeth to play as well as he does. Three decades of sold-out concerts have taken him all over the world, and tonight, his flamenco show `Arte y Pasion' headlines the Hampton Court Festival. But nothing had prepared him for the media whirlwind that struck him when he was outed as a special friend of Tony's. "It was unbelievable," he says, three months later, still shaking his head in bemusement "I was bombarded. Everyone wanted interviews."
But nobody got them. Pena has remained silent. So, as we sit down together in the airy conservatory of his double-fronted north London home, given a Hispanic air by whitewashed walls, creeping flowers and decorative china plates, a sort of intellectual paso doble begins, dancing round the subject of Tony Blair.
First things first: is the Prime Minister any good as a guitarist? Pena, a normally charming, articulate man, falls silent. Eventually he answers, uneasily. "I think so, yes, I feel very strange talking about someone so high-profile." But does he have a natural sense of rhythm with which to convey the throbbing beat of flamenco? Pena smiles. "He is a sensitive person and a musical person. As to rhythm, if you look at his life and ask whether he does things at the right time, you would discover the answer to that.'
Spoken like a politician. And, like a politician, Pena proceeds to set the record straight. He and Tony spent much of their Easter break playing music together. But Pena added: "The Prime Minister doesn't actually play flamenco, and I am not teaching him. He has a general interest in guitar and classical guitar is what he learns. You know, his family has come to my house before. I have known them for several years. My wife Karin is a friend of Cherie, my children know their children, it is just like anyone else."
There is a reason for this discretion. One of the less welcome side- effects of Blair's elevation is the effect it has had upon his old friendships. As the leader has retreated into the fastnesses of No 10, it has been left to Cherie to maintain ties with the outside world. But this, too, can have its complications. In the micro-managed world of New Lab PR, nothing, however innocent or trivial, can be left to chance. No one can be allowed "off-message" - not even Spanish guitarists. Friends of the Penas say that the Downing Street spinners were livid when word got out about the Blairs' Spanish excursion.
Pena, the eighth of nine children, first came to London in 1963. By day, he studied English. At night he earned his keep playing guitar in restaurants, bars and clubs. On Saturdays, he gave flamenco lessons in the basement of the Wigmore Hall, where one of his pupils was a teenage boy called Adrian Lynch, who had ambitions to study the law. In the years ahead, Lynch would become a lecturer in jurisprudence at King's College, London, before joining a barrister's chambers run by a brilliant Scottish lawyer, Derry Irvine.
Though he went back to Spain, he returned to London in 1968 and within months he was making his major concert debut at the Royal Festival Hall as the supporting act for another young guitarist, Jimi Hendrix.
"At the time," Pena recalls, "that was an almost shocking experience. I wasn't at all knowledgeable about him, but he was a very impressive man and obviously a great artist." Hendrix went on to extinguish his talent and his life. Pena was smarter: he married Karin - an elegant, blonde Dutchwoman - raised a family and continued his steady rise.
For the past 30 years he has divided his time between London and Cordoba. Over the years, he became part of an arty, Hampstead set which included Tom Conti, Alan Bates and, through Lynch, Derry Irvine. Paco and Karin managed their business affairs with great care and enterprise, but they became ardent Labour-supporting north Londoners. When they were introduced to Tony and Cherie Blair, it must have been a meeting of like-minded souls.
For Blair and Pena share not just a set of political principles, nor even a love of music, but also a deceptive, authoritarian steeliness. Pena is the leader of a company of musicians and dancers. The glowing reviews which "Arte y Pasion" attracted when it toured Britain last year all remarked upon his self-effacement. The on-stage star was a dazzling young dancer called Angel Munoz, the thinking woman's Joaquin Cortes, but Pena's performers dance to his tune. "I am the director and it is my show. There are a lot of people in it who are very good at what they do. I'm proud of them and I want to show them off, but there is no question that I am the boss and I control what they do."
So, tough on flamenco, tough on the causes of flamenco. But what about his role as a teacher? Pena is a visiting professor at the Rotterdam Conservatory. How does he instruct sober northern Europeans in such hot-blooded music? Once again, he is not afraid of hard choices: "I never take it lightly when I'm passing information on to someone else. If there is difficulty in what I am trying to make them do I don't shy away from that or obscure it. Most of my pupils take it seriously. Others tend to be more interested in the more flashy aspects of the music, or in being themselves. It's almost an ego thing. That is a little battle I have to fight now and then."
As he struggles against the egos of Gordon Brown and Robin Cook, or tries to keep his back-benchers singing from the hymn-sheet, rather than making up their own, bright red descants, Tony Blair must surely know exactly how Paco Pena feels.
Paco Pena's show, `Arte y Pasion', is at Hampton Court tonight at 7.30 (0181 781 9500)