PHOTOS: Rehearsal for London Olympics torch relay

London 2012 organisers, who staged a dress rehearsal for the Olympic torch relay on Friday, received comforting reassurance from a previous host city over fears of protests.

The torches, which will be unlit, will travel by train, road and boat between Leicester and Peterborough in central England.

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A man who was at the heart of the Vancouver 2010 Winter Olympics reassured Britain on Thursday that potential demonstrations are likely to melt away when national excitement takes off during the relay and the Games.

"Typically the whole community comes together around making the Olympics a success," Gordon Campbell, the Canadian High Commissioner to the UK, said from his elegant office in one of London's most prestigious addresses.

"It's all very well to have critics as you go through the process leading up to the Olympics but when you get to the Olympics it's in everybody's interest for them to be a success."

The Olympic flame will visit most parts of Britain during its 70-day tour starting on May 19 before returning to the capital for the opening ceremony at the Olympic Stadium in east London on July 27.

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British police and Olympic chiefs are aware the torch relay and Games could be a magnet for demonstrators keen to draw attention to their message at a time when the world's attention will be on London.

Police warned that attention-seekers, rather than the violent protests which marred the torch relay four years ago, will pose the biggest threat.

One of the most high profile pressure groups campaigning against London Olympic sponsors Dow Chemical, oil company BP and mining giant Rio Tinto, is an environmental coalition called "Greenwash Gold 2012".

Others activists include a trade union protesting against work conditions in factories making Games merchandise and locals trying to halt the building of temporary basketball training courts near the Olympic Park to protect its green areas.

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A lone protester who disrupted the annual university boat race between Oxford and Cambridge earlier this month brought home the danger.

Olympics sports minister Hugh Robertson said he was "pretty horrified" when he saw the man jump into the River Thames.

"It's not entirely new territory (protests) but I just hope that people will not do it during the Olympics because it will be embarrassing internationally but I hope that people watching events will do what they can to discourage people from doing it," he said in a telephone interview.

Campbell was premier of the host province British Columbia during the 2010 Winter Olympics and he faced various protests including by some indigenous groups.

But Campbell said that when the Olympic torch arrived in the country protesters became a small voice among cheering crowds.

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"If you watch a little kid and they see that Olympic torch and it is coming towards them you can almost see the sparkle in their eye and the excitement that they get as it comes," said the silver-haired Campbell.

By the time the Games began, the protests had dissipated.

"On the opening day there were still concerns," he said.

"But by the second there was as much being done to protect protesters as there was to protect the Olympics from the protesters and then it disappeared."