The event was part of the Government’s live events pilot scheme.
Jack Whitehall kicked off the event with a sketch featuring Line Of Duty stars Vicky McClure and Martin Compston, as well as social media sensation Jackie Weaver, who went viral with her contributions to a parish council meeting.
Coldplay delivered a performance of their new single Higher Power from a pontoon on the River Thames, surrounded by hologram dancers and against a backdrop of purple and orange fireworks.
Little Mix made history as the first female group to win the best British group prize.
The group – Leigh-Anne Pinnock, Jade Thirlwall and Perrie Edwards – thanked former bandmate Jesy Nelson and girl groups including Spice Girls who paved the way.
Edwards said: “Guys, we’ve just made history! I’m emotional.”
Pinnock added: “It’s not easy being a female in the UK pop industry.
“We have seen white male dominance, misogyny, sexism and lack of diversity.
“We are proud of how we have stuck together, stood our ground and surrounded ourselves with strong women and are now using our voices more than ever.”
The Spice Girls applauded the win on Twitter, saying: “Congratulations @LittleMix Doing it for the Girls!!”
It was their first Brit win without Nelson, who quit the X Factor-formed girl group in December, saying the high-profile role had “taken a toll” on her mental health.
Dua Lipa took home the female solo artist Brit for a second time.
She announced she would be sharing her trophy with Dame Elizabeth Anionwu, the emeritus professor of nursing at the University of West London.
She said Dame Elizabeth has said there is a “massive disparity between gratitude and respect for frontline workers”.
Lipa - who performed a medley of hits - added: “It’s very good to clap for them, but we need to pay them.
“I think what we should do is we should all give a massive, massive round of applause and give Boris (Johnson) a message that we all support a fair pay rise for our front line.”
She was later honoured with with one of the biggest awards of the night - best album.
She dedicated her second award to Folajimi Olubunmi-Adewole, known as Jimi, who died attempting to save a woman from the Thames last month.
Billie Eilish saw off competition from artists including Cardi B and Taylor Swift to win the international female solo artist gong, while Arlo Parks said it was her “dream to true” to be named breakthrough artist.
Accepting her award, Swift said: “I’m really, really proud to be part of this musical community, especially in a year when we all needed music so much.
“But what we needed even more was the help and support that we got from the NHS and the key workers who are here tonight.
“Thank you for everything that you have done for us.”
Haim beat acts including Run The Jewels and BTS to win the international group Brit Award. Whitehall praised the for making their “dedication” in coming to the awards from America and therefore having to quarantine.
Afrobeats star J Hus also won the male solo artist Brit Award.
Headie One, Parks and Griff were among the performers - with Years and Years singer Olly Alexander and Sir Elton John performing a special rendition of It’s A Sin.
The pair performed a version of the Pet Shop Boys’ 1980s hit, inspired by the Channel 4 TV series of the same name.
The pair were joined on stage by drag queens while Sir Elton’s husband David Furnish delivered an introduction highlighting the work of the Elton John Aids Foundation.
Audience members attending the indoor ceremony were not socially distanced or required to wear face coverings once seated.
However, they needed proof of a negative lateral flow test result to enter the venue and will be required to provide details to NHS Test and Trace and follow Government guidance while travelling.
Ahead of the ceremony, Lipa paid tribute to the late singer Amy Winehouse on the red carpet.
She arrived at the venue in a golden dress with a beehive hairdo in an apparent nod to Winehouse, who died in 2011.
The singer, who is up for three awards, said she was “very excited” to be at the ceremony.
Olivia Rodrigo, who scored a number one earlier this year with Drivers License, said it is her first time in the UK and she has “always wanted to come”.
“It is just such a whirlwind. I feel so lucky,” she said.