Sonic the Hedgehog: What did you do?
Shadow the Hedgehog: What I had to!
Shadow the Hedgehog: When we're done, there won't be anything left.
Sonic the Hedgehog: Hey, no cheat code!
Tom Wachowski: Sonic, you finally found your family. I know it hasn't been easy, but you didn't change who you are in here.
Sonic the Hedgehog: Yeah, in my lungs.
Tom Wachowski: Or your heart.





Answer: Per a quick Google search, it appears there are several locations in London where there are giant screens. He likely was running around the city in a panic (there is a doomsday weapon threatening to destroy mankind, after all) and managed to stumble onto one of the locations.
TedStixon