A group of sniffer dogs are being put at the forefront of preparations for London's Olympics in 2012, taking part in a specialist training programme.
Eight dogs and their handlers have begun a 10-week course at the Metropolitan Police dog training centre in Kent, learning to detect explosives.
The dogs will then gain on-the-street experience before being deployed at airports, hotels and venues in 2012.
Among the eight dogs are labradors, springer spaniels and cocker spaniels.
They, together with their handlers, are being trained to search buildings, open spaces, cars, trains and boats.
One of their first tasks was a classroom-based exercise to search a pile of luggage for explosives.
Once they had located the explosives, the dogs were given a reward - which has to be kept secret for operational reasons.
Another exercise involved searching for explosives hidden in a car.
"The handler and the dog have to display the same sort of qualities," said Insp Alun Jenkins, chief instructor of the centre at Keston.
"They have to be resilient, they have to be tenacious and they have to be very, very patient. Sometimes getting the handlers is harder than the dogs."
At present, the Metropolitan Police has about 350 dogs - of which about 50 are trained to search for explosives. During the Olympics, it is expected that dogs from other police forces will also be made available.
Pc Neil Hurren - who is training with his labrador Libby - said he was attracted to the role because it was a "challenge". But he admitted it was proving harder than he thought.
"It's quite tricky and very technical in places.
"You can let the dog go and it will search and keep searching. But it's about me trying to impress upon the dog the importance of what to search for and where to search for it."