"We're marching for the rights of trans people," says organiser Lucia Blayke at London's first ever Trans Pride.
"For healthcare, for social housing, for education, to stop the deportation of trans refugees in the UK and many other issues."
The event on Saturday saw transgender people and allies marching through the streets of the city.
It was set up because some trans people feel they are sidelined in the LGBT community.
"Trans people don't have the same acceptance as the rest of the LGBT community," Lucia told Radio 1 Newsbeat before the event.
She added it's "the one day of the year trans people can stand in an open space and think: 'Wow, I'm not the outcast'."
A third of transgender people report being discriminated against in public in the last year because of their identity, according to a survey by LGBT charity Stonewall of 871 people.
Almost half of those surveyed say they don't feel comfortable using public toilets for fear of harassment.
"It's still a celebration but we need to have this fire about us to say: no, this isn't acceptable."
Lucia wants the event to remind people of Pride marches in the eighties - which took place during the AIDS crisis.
"Marchers went out there to create social change. They didn't go out there to see Kylie Minogue and have a few cocktails."
Kylie Minogue headlined Brighton Pride this year, where trans people were part of the march and had their own space.
Newsbeat has contacted Brighton Pride and Pride In London for comment.
There were some safety concerns before the event, and the exact route was kept secret in case of violence against the trans marchers.
The organisers worked with the Metropolitan Police and Newsbeat didn't see any trouble on the march.
What does transgender mean?
Stonewall describes a transgender person as someone whose "gender is not the same as, or does not sit comfortably with, the sex they were assigned at birth."
Some transgender people may transition to physically become the gender they identify with, which can include hormone therapy or surgery - but not all trans people do this.
'At Pride, I'm an outsider'
As a trans woman, Lucia support mainstream Pride marches, but they're also places where she feels excluded.
"I go to Pride every year, it's lovely, it's a fun celebration. But the fact is, at Pride I'm still an outsider," she says.
"Every day of my life walking around in public people point and laugh, stare - and sometimes they abuse me. This happens at Pride too."
"It's not the organisers of Pride's fault. It's not the message of Pride. It's just as simple as - we still don't fit in with wider society."
But there are some who believe transgender people get preferential treatment in the LGBT community.
At Pride In London 2018 and Manchester Pride 2019, a group of women staged protests, claiming lesbians are being erased by the "misogyny" of trans-activism.
And they don't support London Trans Pride.
"It's ironic that trans people are seen as needing their own spaces - in Trans Pride and elsewhere," says a spokeswoman for the group Get The L Out, in a statement to Newsbeat.
"They are already centred in LGBT Pride marches and in mainstream feminism."
There is widespread support for the event though - with London Mayor Sadiq Khan saying he is "delighted" that London is hosting its first Trans Pride.
"This event will be a fantastic example of how we celebrate and embrace our rich diversity," he tells Newsbeat in a statement.
"Trans people will always be welcome in our city and I will continue to work with charities, communities and the Met to improve the lives and protect the rights of all LGBTQ+ Londoners."
Trans Pride also influenced restaurant chain Wagamama to introduce gender neutral toilets to 50 of their branches across the UK - despite admitting it's a "subject that not everyone agrees on".
"When London Trans Pride was announced this year it prompted us to really consider whether there was anything we could do to make a meaningful, positive impact on the lives of our transgender and non-binary team members and guests," a spokesman said.
'Our message will inspire change'
"Hopefully Trans Pride will start conversations on health care, public safety, our suicide rates - which are through the roof - our mental health rates, which are not good, and our low employability rates," says organiser Lucia.
A 2018 study quoted by Public Health England suggests that more than 34% of trans adults had attempted suicide at least once.
"I can't think of one example, in the history of the UK, where more than a few hundred trans people have gathered together in public," says Lucia.
"The message that will send out to the world really will inspire change."