Last night's Diana concert was ostensibly a tribute to the late princess on what would have been her 46th birthday. But its deeper function was - yet again - to demonstrate the awesome resilience and adaptability of the monarchy. Those who have doubts about Prince Charles need only look at the next generation, the sons Diana left behind, to see that the institution is healthy, porous to new influence and robust in its attitude to the future. In their lack of polish, their honesty and their charm, William and Harry had the crowd at Wembley, and hundreds of millions at home eating out of their hands. Interesting, too, to note that Harry and Chelsy are much the better dancers: Kate Middleton cannot dance at all, while William does his swaying best, grinning arhythmically. The highlight of the concert ought to have been Sir Elton John, who was indeed majestic: but the laurel must, in truth, go to his warm-up act, Ricky Gervais, who performed the David Brent dance and, with Mackenzie Crook (Gareth in The Office), a memorable acoustic version of Brent's song, Free love on the Free Love Highway. It is a measure of how much time has passed since the Princess's death that The Office was not even a twinkle in Gervais's eye in 1997 and has now, itself, like her life and work, already passed into the realms of nostalgia.