Gong, Queen Elizabeth Hall, London

This is Gong we're talking about, and half measures are an unknown quantity in their world. This is a band that knew what the joke was, and their joyous trip to enlightenment and the left-hand path made for an unforgettable, psychedelic experience at Massive Attack's Meltdown.

Founded in 1967 in Paris by the Australian musician Daevid Allen and the poet Gilli Smyth, Planet Gong has been through many permutations. This 2008 gig reunited Smith and Allen with guitarist Steve Hillage and Miquette Giraudy on keyboards, plus the veteran Gong bassist Mike Howlett, who took to the stage in monk's cowl, and jazz saxophonist Theo Travis. It's a line-up that fans have dreamt of for years, and tonight they delivered two unremitting hours of mind-crushing delight.

From the start, atonal and ambient electronica blew across an empty stage, the iconic Gong mandala of eyes, triangles, and circles hovering on the projection screen behind. Allen sprang out in top hat and tails, long white hair hanging to his shoulders, his stage movements a cross between your great-uncle dancing and weaving a spell.

The band was awesome, wound as tight as a tourniquet in the rhythm section, with both Hillage and Allen playing cosmic, fabric-ripping guitar with fantastic range and feeling. Smyth's space whisper – echoplexing her voice into zero-gravity loops of call and response – worked wonders, while Travis sailed over and under on sax, clarinet and flute.

The set was filled with classic Gong tracks – "Master Builder", "Sold to the Highest Buddha", the glorious "Om Riff", "You Never Blow Yr Trip Forever", Hillage's "Light in the Sky". You left with a string of Gong mantras going round your head: "...have a cup of tea, you can do what you want, why don't you try, You are I or I am you, Hang on to your head..."

The old Notting Hill alternative society used to talk about good drugs (acid and dope) and bad drugs (everything else). It's true, visionary drugs are great to watch Gong by, but failing that, the projections will take you there. A blizzard of strobed imagery – kaleidoscopic, fractal and interstellar – all tore at you at the pace of three or four per second. The visuals matched the music, and for the audience, abandoning their seats for an extended encore, meltdown was inevitable.