Rock opera. Is there a phrase in popular music more likely to bring about a total collapse of the will to live? Probably not - it seems so redolent of pomposity and excess - so tonight's concert counts as a narrow squeak. It was initially billed as a complete acoustic performance of the original 1969 rock opera Tommy - a plan the Who have abandoned, instead playing the album's highlights as an encore. No one in the audience looks particularly distraught at this turn of events. For their main set, the Who play the singles that made them famous: I Can't Explain; Anyway, Anyhow, Anywhere; Substitute. They lunge belligerently forth, a series of sudden, sharp impacts that do not appear to be blunted by the cold that turns Roger Daltrey's voice into a bark, nor by the absence of Keith Moon's unique percussive whirlwind, nor indeed by the presence of Pino Paladino, the characterless session musician's characterless session musician, in place of the late bassist John Entwistle.
Neither of the band's surviving members look particularly like rock legends - in full flight, Daltrey most closely resembles a man confronting a neighbour about branches overhanging into his Essex garden, while Townshend's dark suit, cropped hair and jowly features make him look like Will Self's dissolute great uncle - but their appearance makes their performance all the more surprising. Daltrey attempts to play two tambourines and ends up smashing them both. Townshend runs to the front of the stage, jabs his guitar violently at the audience and windmills his arm in time-honoured style. It should look ridiculous. Instead, it's a thrilling reminder of the unpredictability and menace that underpinned the Who in their prime.
Up in the balcony, a man rips off his shirt and begins miming the drums, while in the stalls, an entire family are frantically pogoing in unison. The Who, it seems, still have the power to move an audience in ways far beyond the standard reverence afforded heritage rock acts.