Gay and lesbian revellers plan to protest against the treatment of gay people from other countries by governments including Britain's at a colourful Pride parade.
The theme of this year's event in London is Fairy Tales, Myths And Legends, and organisers promise "a colourful procession of beaux and beauty, princes and prancers, debutantes and dancers." They expect a turnout of more than half a million.
Campaigners will use the event to voice their anger about what they see as the Government's failure to give refugee status to the gay victims of persecution in other countries.
Harriet Harman, Minister for Women and Equality, will be among the politicians speaking on the main stage in Trafalgar Square at 3pm. But gay rights campaigner Peter Tatchell warned that she was likely to be in for a rough ride.
He said: "One of the biggest issues will be the Government's mistreatment of lesbian and gay asylum seekers."
But the Home Office defended its record on the issue.
A UK Border Agency spokesman said: "We consider each case on its individual merits and will continue to provide refuge for those asylum seekers with a genuine need for protection."
Festival-goers will also draw attention to the persecution of gay people in countries such as Iran, Jamaica, Nigeria and Uganda.
Mr Tatchell himself plans to carry a placard mocking Iran's President Mahmoud Ahmadinejad, in protest against the country's treatment of its gay population.
His placard will depict a doctored photo of the Iranian leader wagging his finger while wearing make-up and jewellery, accompanied by a caption accusing him of being a murderer and homophobe.
Read More
MORE ABOUT