Photo: British Transport Police

An estimated 1 million visitors are expected to travel to London for the 2012 Olympic Games, and with large crowds comes the threat of a terrorist attack. The city is preparing for this influx of people in a variety of ways, and bomb-sniffing dogs are one of its first lines of defense against the threat of an attack.


The British Transport Police, which protects Britain’s subways and railways, is the largest and oldest dog unit in the United Kingdom, and it’s been using “proactive” dogs to guard London’s transportation system for years. These canines focus on inspecting specific places within in the transit system and investigating suspicious luggage left on trains or buses.


However, three years ago, the BTP began training “passive dogs,” which search for explosives among crowds. These dogs zero in on suspicious scents and follow them to their source. About a dozen passive bomb-sniffing dogs have been incorporated into the BTP’s 60 highly trained-dog force over the last three years.


Bomb-sniffing dogs are scent-trained to recognize a variety of smells associated with explosive devices. When they pick up on a scent, they seek out the source and then beside it and await their reward, which is typically a favorite toy. During a recent drill in London’s St. Pancras railway station, Benson, the black Labrador pictured above, successfully sought out a police officer carrying explosives and was rewarded with a tennis ball.


“The dogs are an extended part of the security operation within London and around the country, making sure the railways are safe, members of the public are safe and that we can keep all the transport system open,” British Transport Police Inspector Ed Purchase told MSNBC.


The U.K.’s alert level is expected to be raised to “severe” during the Olympics, which means that an attack is highly likely, and the games will see the country’s largest peacetime security operation involving thousands of security officials. The city of London estimates that 13,500 military personnel, 12,000 police officers and 10,000 private contractors will be involved in the event’s security operations.


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