Carnival is the largest street festival in Europe, and happens every year in London's Notting Hill (yes, the neighbourhood made famous by that movie). The last few times I've been to Notting Hill, it's been to visit it's famous Portobello Road Market. But Carnival radically transforms the place from bustling market and stately pastel homes, to a pulsing street party.
Carnival has been around since 1964 and is an important symbol of communities coming together, and a way for Afro-Caribbean-Londoners to celebrate their heritage and culture. The very first carnival was an attempt to showcase the steel band musicians who played in the Earls Court of London every weekend. When the bands paraded through the streets of Notting Hill, they drew black residents out on to the streets, reminding them of the Caribbean homes they had left behind.
This year it was particularly important in light of the widespread riots earlier this month. London's police and government had to prove that London could pull off a large event without more riots - especially with pressure mounting with the Olympics coming to London next year. To keep everything under control, London deployed over 6,000 police officers to Notting Hill, with extra officers posted around the city.