The rejuvenation of a classic rock titan can be as exhilarating as the discovery of a new one. Purists may say that the Who died when Keith Moon did, and question whether Paul McCartney and Ringo Star

The rejuvenation of a classic rock titan can be as exhilarating as the discovery of a new one. Purists may say that the Who died when Keith Moon did, and question whether Paul McCartney and Ringo Starr would dare to go out billed as the Beatles. But this group, and its mercurial muse, has rediscovered its creative center with a verve that renders any such haggling somewhat academic.

So it is that an almost unrecognizably upbeat and engaged Pete Townshend and a preposterously well-preserved Roger Daltrey are bringing the live, and enlivened, version of the Who legend into the vision of yet another dynasty of inquisitive fans. The current Who tour, featuring such live stalwarts as John "Rabbit" Bundrick on keyboards and Zak Starkey on drums, is eating up the road miles around the U.K. and Europe with a rapacious appetite. There's even a new album, the band's first since 1982, in the final stages.

At Hyde Park, exactly a year on from their impressive contribution to Live8 in this very space, the band topped the bill of the second day of Hyde Park Calling, a new addition to the live calendar that had seen Roger Waters performing the night before. The Sunday bill, amid blazing sunshine, included Razorlight, the Zutons and Ocean Colour Scene on the main stage, with a covered second stage offering Primal Scream and the Casban Club, the band featuring former Jam bassist Bruce Foxton, two ex-members of Scottish riffmeisters Big Country, and Townshend's brother Simon at the vocal and songwriting helm.

Somewhere after 8 p.m., the Who came roaring out of the traps with "I Can't Explain," which like many of its peers was restored to something approaching its original joyous energy. With Daltrey ever the dependably energetic frontman, the variable in any Who show has been Townshend's mood, especially in recent years. Here, as per all recent sightings, he was relaxed, funny, generous and committed.

The set was based squarely on the Who's unassailable catalog. The absence of live staples such as "5.15" and "You Better, You Bet" was noted, but in such a powerful show, not unduly missed. Daltrey would later pass the intense vocal examination of "Won't Get Fooled Again," but was also up to the more consistently challenging task of mastering "Love Reign O'er Me."

The new era which these shows potentially ushers in was represented by "Real Good Looking Boy," the fresh inclusion on 2004's "Then & Now" compilation, and by one selection from the upcoming album, "Mike Post Theme." Largely acoustic, lyrically diverting and quite studious, it was hardly a rock anthem to accompany their time-tested greats, but it showed considerable promise, and a crowd that included a notable representation of new teenage admirers was suitably impressed.

As they completed the set, Daltrey said good-humoredly, "You'll never look at your dad in the same way again." They may now be working in someone else's generation, but no one's trying to put the Who down.