More than 5,000 police officers will take to the streets today for the Notting Hill Carnival as Scotland Yard faces its biggest public order test since the riots.
More than a million revellers are expected to descend on the capital over the coming days for Europe's biggest street festival.
An unprecedented security operation will see record numbers of police officers on duty with London's reputation at stake in the wake of widespread violence and looting earlier this month.
Police chiefs launched their "robust" strategy against troublemakers by making more than 40 pre-emptive arrests and agreeing an earlier finish time with organisers.
Commander Steve Rodhouse said he was "really confident" he has the resources at his disposal to protect the two-day event.
While 5,500 officers will be on patrol in the carnival area today, this figure will be beefed up to 6,500 tomorrow.
Elsewhere in London there will be more than 4,000 additional officers "as well as the thousands who are normally on duty", Mr Rodhouse said.
London Mayor Boris Johnson has issued a rallying call to "let the true spirit of London shine through", hoping the carnival will help heal wounds left by the riots.
"It's right that carnival goes ahead so we can show the world that the overwhelming majority of London's people are decent, law-abiding citizens who respect the law, love their city and want to celebrate our vibrant, diverse and historical culture," he said.
Mr Rodhouse accepted this year's event takes place in "unusual and exceptional circumstances".
The police chief said troublemakers were plotting disruption via social networking technology.
He said the "degree of chatter" surrounding trouble-makers was consistent with previous years - despite thousands of arrests in the wake of the wave of looting and violence that gripped England a few weeks ago.
"Our intelligence picture is still being developed as we approach the weekend and it will be kept under review right up to and indeed during the carnival itself," Mr Rodhouse added.
"At this stage it would be fair to say we do have intelligence that some gangs do want to come to the carnival and create trouble for us."
Road closures were to be in place around the carnival site from 6am.
A total of 2,082 people have been arrested in connection with rioting this month and some 1,191 suspects have been charged, Scotland Yard said.