The red carpet is rolled out tonight for a star-studded London premiere. The crowds will cheer not a new movie but Halo 3, the computer game tipped to outperform Hollywood blockbusters.

Jonathan Ross and Pharrell Williams will join hundreds of fans at the London iMax cinema tonight for the unveiling of Microsoft’s weapon in the console wars.

Halo 3, the final chapter in the futuristic game designed for the Xbox 360, could achieve the biggest opening for any entertainment product.

The first two instalments sold more than 15 million units. Halo 2 recorded opening-day sales worth $125 million (£62 million). Every day tens of thousands of people play an online version of the game, in which a space marine called Master Chief fights an alien army called the Covenant.

Westminster City Council blocked a midnight launch on Oxford Street fearing that the crowds would be overwhelming, but 1,000 UK retailers will be opening at midnight for the release.

Halo 3 has the production standards of a Hollywood blockbuster and is expected to generate multiplex-style profits. A spokesman for Xbox said: “The expectation is for sales to match the opening weekend of a Spider-Man or Pirates of the Caribbean.”

Spider-Man 3 grossed $151 million (£75 million) on its opening weekend and cost £250 million to produce and market, whereas Halo 3 cost around £30 million for a team of 300 programmers to develop. Analysts predict that it will generate around £450 million for Microsoft.