The Metropolitan Police have said it will be using greater search powers after a man was stabbed at the Notting Hill Carnival.
The victim’s injuries are not life-threatening, the Met said.
Police have made 38 arrests across the carnival and four knives have been recovered.
“While the majority at today’s event have come to enjoy themselves, a number of people regrettably have not,” the force said in a statement.
A Section 60 order was issued on Sunday night, giving officers the power to demand the removal of face coverings being used to conceal a person’s identity and anyone refusing can be arrested.
Around 7,000 officers are on duty for the bank holiday weekend event after the force said there would be a “very significant policing presence” this year.
Around a million people are expected to attend Carnival, with Sunday kicking off proceedings in earnest with Children and Families’ Day.
Carnival is billed by its organisers as “the greatest community-led event on the planet”, and began in the 1960s to unite London’s diverse communities.
It is one of the longest-running street parties in the UK and is free to all, celebrating Caribbean culture with vividly costumed performers in a parade through the streets with dancing and music.
Matthew Phillip, chief executive of the Notting Hill Carnival, said ahead of this year’s festivities that the rioting and violent disorder in the wake of the Southport stabbings earlier this month “highlights why Carnival is set up in the first place”.
He said: “Carnival is the biggest celebration of inclusion, and social cohesion that there is in the UK.
“It was set up to bring communities from diverse backgrounds together and it’s still doing that almost 60 years later.”
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Earlier on Sunday, the streets of west London came alive with colour, costumes, dancing and music and thousands of revellers enjoyed the celebrations.
Youngsters were dancing in the streets along the parade route wearing bright and intricate costumes.
The annual celebration of Caribbean heritage, arts and culture has been running for more than 50 years.
The main parade is held on Monday, described by organisers as the climax of the carnival with “party vibes”.
In the past two years, there have been more than 500 arrests at the Notting Hill Carnival as well as 15 stabbings including one death, and more than 125 police officers have been assaulted.