Actor Christian Slater joined Williams on the red carpet, along with a host of UK celebrities including urban music duo the Mitchell Brothers, model Kimberley Stewart and Big Brother's Chanelle.
The launch event was hosted by MCV awards host, TV presenter and self-proclaimed gaming fanatic, Iain Lee.
The night also saw a face off between Pharrell Williams and MySpace competition winner, Mark Webb, over Xbox Live with other celebrities from across Europe including Carmen Electra in Paris and LL Cool J in Amsterdam on the IMAX's cinema screen.
A few technical issues meant that the blue team walked all over the reds, Microsoft's Steven McGill announced that everyone attending would receive a free copy – which was met with an appreciative roar.
The event preceeded this morning’s retail rush for copies of the much-hyped game, which Microsoft expects to become the ‘biggest entertainment launch in history’.