Underworld star Rick Smith has been taken ill after the dance act masterminded the music for last night's three-hour London 2012 opening ceremony.
Smith cancelled pre-arranged media interviews at the BT London Live show in Hyde Park.
A spokesman for the event said: "Rick is unwell today due to exhaustion."
Last night's spectacular launch featured a medley of British pop over the decades with bursts of the Beatles, the Jam, Sex Pistols and Dizzee Rascal.
There were also excerpts from the Kinks, Frankie Goes To Hollywood and Mud's Tiger Feet before Emeli Sande sang the cup final classic Abide With Me.
Smith and Karl Hyde make up the electronic act Underworld, best known for their anthemic hit Born Slippy.
The ceremony's artistic director, Danny Boyle, previously worked with the pair on his films Trainspotting, The Beach and A Life Less Ordinary as well as his production of Frankenstein at the National Theatre.