The Boston bombings have raised fears about the world’s biggest marathon, which takes place in London next Sunday.

“It makes you do a double-take on the whole thing. And I just pray that everybody will be safe,” says Hannah Carter, one of the 36,000 runners scheduled to take part.

The British government insists that the runners and the half a million spectators expected to line the route will all be totally safe — thanks to the U.K.’s expertise in security. Those skills were honed fighting IRA terrorism for more than 30 years in Northern Ireland. They were further refined  by the experience of staging the Olympics in London last year. The U.K. spent a billion dollars on security at the Games, which has also left it well equipped technically.

“The technology, things like CCTV cameras and the software that can automatically recognize odd behavior in crowds, is still state of the art,” says Jennifer Cole, a terrorism expert at the Royal United Services Institute.

London has an estimated 400,000 closed circuit television cameras, more than any other major city.

London is already bristling with security personnel; thousands of soldiers and police officers will be officiating tomorrow at Margaret Thatcher’s ceremonial $13 million funeral. Their security operation could be extended — at no great extra cost — to cover the marathon.

“There are personnel around and processes in place that are going to be very easy to just carry on over into the weekend,” says Cole.

Another analyst, Dr. Peter Lehr — a terrorism studies lecturer at St. Andrews University in Scotland — says there is a much safer and cheaper way to stage the London Marathon. You have the competitors running round and round inside Wembley stadium, behind locked doors, and without any spectators.

But, he says, the only winner would be terrorism.