Thousands of people are set to take to the streets of London for the annual Pride parade, amid increased security.
The event takes place two weeks after a mass shooting at a gay nightclub in Orlando in Florida, in which 49 people were killed.
After the attack, Scotland Yard vowed to up the visible police presence in London on Saturday in a bid to provide reassurance.
The usual celebratory atmosphere featuring song and dance will stop for a one-minute period of reflection this afternoon in memory of the Orlando victims.
It is expected there could be a bigger attendance this year, with people keen to show support for the Lesbian Gay Bisexual and Transgender community.
Campaigner Peter Tatchell, who was involved in organising the first Pride and will take part in his 43rd parade, said people must unite against hate.
He said: "In the wake of the horrific mass murder of LGBT people by an Islamist gunman in Orlando, we are highlighting the need for dialogue, unity and solidarity between the Muslim and LGBT communities - to oppose all hate."
Met Police commissioner Sir Bernard Hogan-Howe has urged people to "take reasonable precaution" but added there is no intelligence to suggest there is a planned attack on London or the march.
This year more than a hundred Met officers will take part in the parade, which will also feature more than 200 military personnel.
For the first time there will be a Red Arrows flypast, in an effort to show support within the Armed Forces for the LGBT community.
Almost 300 groups including charities, religious organisations and businesses, are due to take part in the parade, which is known for its vibrancy and colour.
Participants will leave Portland Place at 1pm and follow a route to Whitehall.
The Mayor of London Sadiq Khan will address the crowd, who will also be treated to performances by Britain's Got Talent judge Alesha Dixon and former X Factor contestant Jake Quickenden.