Metal-detecting knife arches are to be installed for the first time in parts of west London for this weekend's Notting Hill Carnival.
The move comes as the highest number of police officers in six years will also be called up for the event.
Scotland Yard hope the "tried and tested" method will put off people trying to attend the parade while carrying knives or other weapons.
"The Met seeks to support Notting Hill Carnival Ltd, Carnivalists and local communities to deliver a safe and spectacular event over the bank holiday weekend," said Commander Dave Musker, police gold commander for the event.
"Our continued major effort directed against violence across the capital will continue."
He added: "Let no one be in any doubt that if you have the intention to come to carnival and be involved in crime or violence, my officers will robustly and proactively target you to keep Londoners safe."
The police force did not say where the knife arches would be located but said that not everybody would be expected to go through them.
About 13,000 officers are set to police the annual two-day event, which comes to an end on bank holiday Monday. The figure is 450 more than the number of officers deployed last year.
Nearly 7,000 officers – some from the force's Violent Crime Task Force – will be present on Monday to "combat the threat of violent crime" – 900 more than the 6,100 that will be on duty on the less busy Sunday event.
3:01Undercover police and officers from the firearms and dog units will also be at the carnival, which attracts more than a million people each year.
Superintendent Elisabeth Chapple called on those who knew of anyone planning to cause trouble to call police.
More from Notting Hill Carnival
She added: "Whilst there's no specific threat to this event, we are keeping the situation under constant review."
The increased security follows a wave of violent crime in London in recent months.
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