Revellers flooded the streets of west London on Sunday as Notting Hill Carnival began amid scorching temperatures.
Scores of people took to the streets for the carnival's family day, with the mercury reaching 32C in the afternoon. It is thought to be one of the hottest carnivals ever.
Onlookers gathered on pavements in the sunshine as the community celebration carved its way around west London in a mass of music, dancing and bold costumes of neon Lycra and brightly-coloured feathered headdresses.
More than one million people - and thousands of police officers - will be at the carnival over the course of Sunday and Monday.
Mayor of London Sadiq Khan told Sky News there could be a record number of people at the carnival: "We think over today and tomorrow, there could be up to two million people. Everyone is having fun."
A large security operation is in place, including "significantly more" knife arches than last year, to deliver what the Met hopes will be a "safe and spectacular" festival.
But it comes as figures obtained by HuffPost showed arrest rates over three years at the carnival were almost identical to Glastonbury Festival.
Over that time period there were an average of 3.76 arrests per 10,000 people at the carnival, compared with 3.1 arrests at Glastonbury.
The number of police officers at this year's carnival - 12,427 - reflecting the number of shifts worked over the course of the weekend, is slightly down on last year.
Officers will be supported by about 900 event stewards on Sunday and approximately 1,100 on the typically busier Monday.
Ahead of the annual celebration, the Met's Supt Elisabeth Chapple said: "We want to make sure that it's safe and spectacular so we're using a range of tactics including screening arches, using dogs, firearm teams and others.
"We found last year that the use of screening arches alongside other tactics and other teams that were used were really, really effective and so the number of arches has been increased this year."
She said the arches are a "fantastic deterrent" and also help the detection of offensive weapons.
Arches were used for the first time at the carnival in 2018 and detected offensive weapons including knives and other metal objects, she said.
While she did not say how many arches there would be or where they would be positioned, she confirmed there would be "significantly more" than last year.
Last year there were two non life-threatening stabbings over the carnival weekend and 45 police officers were injured.
Supt Chapple said the force will be "taking every step to make sure that doesn't happen this year".
Matthew Phillip, the carnival's executive director, said crime is "quite a small statistic in relation to the scale of the event" and said he wanted to highlight the positives around carnival, describing the longstanding event as a "symbol of community cohesion and unity".
In a message to anyone who may attend the event with a weapon or the intent to commit a crime, he said: "Don't come, you're not welcome."
He said visitors this year can expect more "amazing costumes" and "wonderful food".
Ms Chapple advised carnival-goers to be prepared for very hot weather by taking water or refillable bottles and downloading the official carnival app.
She said: "You can find medical points, food stops and receive live updates on transport network delays."
Met Office forecaster Craig Snell said: "People certainly need to bring plenty of water with them and slap on the suncream."
Again this year there will be 72 seconds of silence on both days in memory of those killed in the Grenfell Tower fire in 2017.
The tower block is within half a mile of the parade route.
