Embracing fellow peace activists at the British Embassy, Mr Kember exclaimed: “I’ve just found out I’ve been released. It must be true — it’s on the news.” He and the two Canadians who had been held hostage with him, Jim Loney, 41, and Harmeet Sooden, 32, spent an emotional hour with fellow members of the Christian Peacemakers Team.

Most of the time was spent “hugging and sharing vanilla and chocolate ice-cream”, Anita David, one of the activists, said. “There were tears, smiles and laughter.”

The only painful moment was when the activists had to tell the three hostages that their American colleague Tom Fox, who had been separated from them 40 days ago, had been murdered. “They didn’t know what had happened to him and it has come as a horrible shock,” Ms David said.

Mr Fox’s handcuffed, bullet-riddled body was found on March 9, dumped in a street not far from where the peace activists were rescued in yesterday’s dawn raid.

The long-awaited breakthrough that ensured Professor Kember and the two Canadians were spared a similiar fate came late on Wednesday night when one of two Iraqi men picked up by US troops during a raid in the capital revealed where the three were being held. Officials in Baghdad and London were saying little about the genesis of the operation, but it is thought that the young Iraqi had been under surveillance for several days and his capture was more than mere good fortune.

For months a secret unit known as Task Force Black, commanded by a senior SAS officer, has been quietly hunting Iraqi war criminals and searching for hostages.

Task Force Black is a combined team of about 250 US, British and Australian special forces backed up by intelligence personnel. After the hostages were snatched while leaving a mosque in western Baghdad last November, Scotland Yard also sent in trained negotiators, the Canadians flew in their kidnap experts, and FBI agents and MI6 officers were in Baghdad trying to make contact with intermediaries who could put them in direct touch with the kidnappers.

British undercover troops, bearded and dressed as Iraqis, met religious leaders and tribal elders to piece together scraps of information about the hostage-takers, who called themselves the Swords of Righteousness Brigade. Satellite photographs, telephone intercepts and reams of other information were examined in minute detail. Intelligence officers followed up dozens of tip-offs from paid informants, community leaders and Iraqi police, but all leads had proved false until the detainee betrayed his crucial secret.

The SAS had narrowed down the likely location of the kidnappers’ base to the scruffy suburbs of western Baghdad around al-Hurriyah, a stronghold of mainly Sunni insurgents and criminal gangs responsible for dozens of abductions of Iraqis. The detainee disclosed the precise address, describing the location and making sketches of the house and the nearby roads.

For weeks the special forces had practised strategies for taking kidnappers by surprise. They used mock-ups of various types of properties, unsure if the hostages were held in a basement or in a house where children lived. Now they had to act fast. Their concern, according to one source, was that the hostage-takers might realise that one of their gang had been captured and kill the three Westerners before escaping.

At about 3am yesterday the SAS squadron commander in charge of the rescue force summoned his team at their base inside the heavily fortified green zone. The force consisted mainly of SAS troopers, backed by about 50 soldiers from the 1st Battalion The Parachute Regiment and Royal Marines — all members of the Special Forces Support Group codenamed Task Force Maroon.

Defence sources told The Times that helicopters with reconnaissance cameras and Predator unmanned aerial vehicles, which can monitor movements on the ground from 20,000ft, were deployed. The men who spearheaded the rescue arrived in a convoy of cars disguised as local taxis and pick-up trucks.

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