6 October 2011 Last updated at 20:26 ET

London 2012: "100 days of peace" campaign is launched

Jimmy Mizen was murdered in a bakery in 2008, and his brother is asking for 100 days of peace

The Olympics must be remembered "for peace as well as sport", the brother of a teenager killed in London has said.

George Mizen, 12, is joining thousands of British children from nearly 500 Catholic schools in London, Essex, Kent and Hertfordshire to call for "100 days of peace" around next year's Games.

The schoolboy lost his brother Jimmy, 16, when he was stabbed at a bakery in Lee, south-east London, in May 2008.

A mass will be held at Westminster Cathedral later to launch the campaign.

It will be attended by George and his parents, Barry and Margaret, plus about 1,400 pupils, some of whom come from the areas of London worst affected in the riots in August.

The Archbishop of Westminster, Vincent Nichols, will tell them that he applauds the many young people with an "immense desire for peace".

He will also encourage them to spread the message of peace throughout summer 2012.

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He will say he is "immensely proud of the character and leadership of so many young people in our schools as they work for peace and safety on our streets".

"We see and celebrate their generous contribution in varied ways to the alleviation of poverty, their reaching out to those others have cast to the edges," he is expected to add.

The service will end with each child being given a special booklet on peace.

George Mizen said he thought it was important "for people to try and become friends with each other, and I hope the 100 days of peace will do that".

"I also hope that the 2012 Olympics will be remembered for peace as well as sport," he added.