Security Serivce MI5 once planned to recruit a team of specially-trained gerbils as a secret weapon to sniff out spies, it has been revealed.

The animals were to help interrogate suspects because they could use their acute sense of smell to detect a rise in adrenalin - the chemical released in sweat when people feel under stress.

The security service's director general Sir Stephen Lander revealed the plan was considered during the 1970s when he spoke at the launch of a new spy exhibition in London.

But MI5 dropped the plans after it was discovered the gerbils could not tell the difference between terrorists and passengers who were scared of flying.

Israeli idea

MI5 archives contain a complete volume on the idea, which would have played a key part in interrogating suspected spies.

Sir Stephen said research for the Royal Canadian Mounted Police had uncovered the gerbil's skill and the Israelis had first put it to the test, he said.

They had kept the rodents in cages next to security check areas in Tel Aviv airport.



