Despite fears that Pride London, which also incorporates World Pride 2012, would be cancelled due to funding problems, it has been a huge success.
Gay human rights campaigner Peter Tatchell, who helped organise the first Gay Pride in Britain in 1972, said that despite the problems and setbacks, the numbers at today's events were huge and the atmosphere amazing.
It's much more political than in previous years. The global human rights message is really strong for lesbian, gay, bisexual, and transgender freedom.
Nearly 80 countries still criminalise homosexuality with the penalties ranging from life imprisonment and even execution.
We are also celebrating 40 years of Gay Pride in Britain. In those last four decades we have won the appeal of nearly every anti-gay law. All that remains is to win same sex marriage."
Prime Minister David Cameron has also added his support for the event.
The UK has been judged to be the best country in Europe in which to live if you're gay so it is great that World Pride is being celebrated here in London - especially during this Diamond Jubilee and Olympic year.
I'm very pleased that the Mayor of London has enabled the march and events in Trafalgar Square to go ahead and I want to thank all the volunteers who will be stewarding the event and contributing to it.
It is 40 years since people first marched in London calling for equal rights. Since then we've come a very long way and progress is still being made."
More top news
A trainee detective who sued Essex police for a prank which went wrong and left her injured has won damages.
Munir Mohammed enlisted pharmacist Rowaida El-Hassan to advise on chemicals for a bomb after they met on dating website SingleMuslim.com.
The collection includes hundreds of items of refugee clothing found mainly on beaches of Lesbos and garments left behind in Calais.