The Oxford Street branch hosted the official launch, which saw 750 customers queuing to be among the first in the country to buy the game.
Attendees were offered the chance to win official merchandise as well as a Samsung TV on the night.
The first person in line was 27-year-old Mad Sirman from London, who had started queuing at 5pm on Friday.
Modern Warfare 3 is available worldwide on Xbox 360, PlayStation 3 and PC now.
> Read our review of Modern Warfare 3
> Modern Warfare 3 price round-up: £9.99 with trade-ins
View images from Modern Warfare 3's official Oxford Street launch below: