Thirty years after they formed their ugly, irresistible, lumbering riffs are still influencing rock music like no one else save the Beatles. After all, what were Nirvana but the perfect blend of the Fab Four's sunny melodism and Sabbath's grinding pessimism. Having reformed for a lucrative American trek, this show promised to be the capital's last chance to view the original classic line-up.
The last few years have been kinder to Osbourne than his erstwhile band mates, despite the indignities visited upon him by a Channel 5 special about his home life, where his well-spoken children chided him for using bad language. Sacked after his recreational habits became a liability, the supposedly washed-up singer went on to huge solo success in the US. Although this reunion may whiff of financial expediency for all save the front man, it's a unique opportunity to see a living, breathing Seventies hard rock act in the flesh.
Opening with "War pigs", the entire hall is chanting along as Ozzy, healthier these days, leads them. To his left, Iommi, sporting the louche look of an art teacher given to holding "private tutorials", alternately torments and caresses his guitar - never producing less than a huge noise. Geezer Butler beats his bass, head nodding throughout and drummer Bill Ward, introduced by Ozzy as "nearly dead", pummels the kit as if he is trying to banish all thoughts of retirement. Because it's hard to imagine them, especially Ozzy with his endearing habit of clapping out of time, doing anything else.
The set consists entirely of material at least 20 years old, yet who can deny the thundering charm of the cautionary "Fairies Wear Boots", that tribute to "Sweet Leaf" (not about PG Tips) and the clumsy epic "Snowblind".
But the choice of tracks is hardly relevant. The songs are ridiculous, the band knows it and the audience, brightly lit throughout, know it too. But the performance and the reaction are sincere. Irony has never sat well with Heavy Metal. But entertainment values do.