Police officers with special skills for recognising the faces of offenders will be monitoring Notting Hill Carnival in a crackdown on crime.
The "super-recognisers" will be inside a CCTV control room seeking out both offenders committing crimes and anyone with bail conditions which ought to stop them from attending the event.
It is one of a number of measures the Met will be taking to ensure visitors from all over the country can stay safe and enjoy themselves during the carnival, which will be marking its 50th anniversary on Sunday and Bank Holiday Monday.
Sunday will start at 10.30am with the colourful parade for Children's Day, and Monday will be the traditional Grand Finale.
The force will also be trialling a facial recognition system to help identify wanted offenders, by using cameras which scan the faces of those passing by and flag up potential matches against a database of custody images.
London's "threat level" has been set at "severe" for some time now and the police are urging all those planning to attend the carnival to remain vigilant and report anything suspicious.
Over the last week, police have arrested 215 people they believe planned to use the carnival as a cover for committing crime or violence. More than 200 search warrants were also made.
Although the arrests were mostly for drugs-related offences, officers have also taken six firearms and 50 rounds of ammunition, as well as a number of knives and machetes from the streets. Three motor vehicles and £30,000 were also seized.
Superintendent Robyn Williams said: "This weekend is the highlight of the year, not only for the Caribbean community, but also for many visitors from London and the rest of the country.
"The Met has worked hard to ensure that Carnival is a safe and enjoyable weekend for everyone who attends and I would ask all carnival-goers to enjoy this family event and make sure that you follow officers' and stewards' instructions."
His tips for staying safe at the carnival include:
:: Checking public transport in advance using the TfL website to avoid stations which may be closed or exit-only;
:: Going with the flow of the crowd, instead of against it, even if police mark out a longer route. Officers will also be handing out maps of the area at the event;
:: Having a set meeting place in case you lose family or friends, rather than rely on mobile phones;
:: Avoiding bringing valuables or too much cash and always being conscious to keep them out of sight, to avoid tempting opportunistic thieves;
:: Staying alert all the way home, even when the party is over;
Police have also asked people to be on the lookout for a missing teenager, who they believe may attend the carnival;
Veronica Sbircea, 15, was last seen around Brixton Road in south London on the afternoon of Thursday July 28.
Veronica, who sometimes goes by the name of Rachel, went missing from Kettering, Northamptonshire, but is originally from London. She is described as white, 5ft and with long straight black hair and brown eyes.
Detective Inspector Stuart Hitchon of Northants Police said: "It's very concerning that for someone who is very active on social media and was seen on public transport several times in the 24 hours before she went missing, there is absolutely nothing since. This clear absence of any activity is very worrying and we really need her to make contact."