Up to 1.5 million people are expected to take to the streets of London for the Pride parade.
Starting at Portland Place, the parade will move across Oxford Circus and go down Regent Street before arriving at Whitehall via Trafalgar Square.
This year’s event celebrates 50 years since the first Stonewall uprising in New York.
London Mayor Sadiq Khan said he hoped it would be the biggest Pride event to have been held in London.
More than 30,000 people from 600 groups, organisations and businesses will take part in the event which this year has a theme of Pride Jubilee.
The Red Arrows carried out a flypast at 13:25 BST.
“The great thing about Pride in London is we can celebrate our diversity and it’s also a good chance for us not from the LGBT+ community to be allies, and to be proud allies,” he said.
“It’s really important that we celebrate the diversity of our city and I want today to be the biggest ever and I think it will be.”
Don Pepper, who was at London’s first pride event said it was very different then.
“There was no dressing up, there was no drag – it was just everyone dressed normally,” he said, adding that there was probably about 1,000 people marching then.
“There was abuse from cars whereas now people cheer you on but then they would tell you to disappear. There wasn’t any entertainment afterwards, we just sat down and had a picnic and that was it.”
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