A spate of robberies is expected across the borough tonight as thugs take advantage of the number of young trick or treaters hitting the streets in search of sweets.
Police will be stepping up patrols to combat the annual rise and are warning residents to keep their wits about them.
Last year robberies in the borough on Halloween jumped to 21 from just four the day before, then fell to 12 the following day.
And in 2006 the figure climbed to 28 from 10 the day earlier before dropping to six after the festival.
Inspector Andrew Deane explained that youngsters were those most commonly targeted as well as most likely to be carrying out the crimes.
He said that, although the ages of victims last year ranged from 12 to 36, it was those aged 12-17 that were most commonly attacked.
The muggers were aged from 12 to 53 but it was mainly those aged 14 to 18 who committed the robberies.
He added: "It's a seasonal rise which is a problem all across the Met in the period covering Diwali, Halloween and bonfire night.
"Halloween is celebrated more and more and young people do get targeted by opportunists in the carnival atmosphere with so many people out.
"The majority is low level, with people getting their goody bags taken, things like that. But there is a number of more serious street robberies where suspects use the festivities as a cover, such as using masks to hide their faces."
He said police were stepping up patrols throughout the borough during the period and officers are educating children about personal safety at their schools.
He added: "There are key steps young people in particular should take. They need to be mindful of their environment, to choose a safe route, and to be discreet with their valuables."
And it is not just the young who can feel vulnerable on Halloween, the elderly can also feel targeted as they are visited by endless trick or treaters.
Help the Aged and Childline have released a leaflet about how pensioners can feel more secure and on responsible trick or treating.
Help the Aged spokesman Alan Burnett said: "It can be a particularly stressful time for some older people, especially those in poor health or living alone."
The charity suggests keeping the door chain on and inviting friends or family around.