As the family of kidnapped Briton Kenneth Bigley were last night waiting to hear his fate, Nick Morrison looks at how hostage-taking has become one of the favourite weapons in the terrorist armoury.

IT takes less than 48 hours for the videos to make their way onto Baghdad market stalls. The camerawork is blurred and jumpy, but the scene has a chilling familiarity. Sometimes blindfolded, often wearing an orange jump-suit, the man sits on the ground in front of maybe four or five men, all masked and clad in black. The man in orange gives his name and nationality, before his head is sawed from his body with a knife.

Among all the images of carnage to have come out of Iraq over the past year, of human lives and buildings destroyed by missiles and suicide bombs, few have had the impact of the pictures of hostages being beheaded by their captors.

Now it is the turn of Kenneth Bigley's family to fear the worst. The 62-year-old was one of three men working for a Middle East company who were kidnapped in Iraq last week. His two colleagues, Americans Eugene Armstrong and Jack Hensley, have both been beheaded, with footage of Mr Armstrong's execution broadcast on a website on Monday.

The kidnappings have exposed the dilemma facing both families and governments in the face of ruthless opponents who will not hesitate to butcher their victims.

In the last six months, more than 100 foreigners have been kidnapped in Iraq, including aid workers, contractors, journalists and soldiers, with 29 of them murdered so far. The kidnappers' demands have ranged from a ransom, to withdrawal of troops or a company from Iraq, to the release of prisoners. The group holding Mr Bigley has demanded the release of the two Iraqi women held in US-run prisons.

"The reason they are targeting civilians is they are a soft target," says David George, lecturer in Middle Eastern studies and terrorism at Newcastle University. "Comparatively speaking, it is difficult to hit British and American troops, so they are going for softer targets.

'The least well-defended targets of all are the queues standing outside police stations, but after that you have the foreigners who have temporary residence in Iraq."

It is easy to see the attraction of kidnapping for militant groups, particularly in a conflict where they are outgunned by superior equipment and numbers. The chances of achieving their objectives may be slight, but the propaganda value, in striking fear into the hearts of potential victims and of being seen to strike a blow against the enemy, is enormous.

While large scale atrocities might cause more devastation, the terror on the face of a single hostage can be easier to comprehend. And with footage of executions posted on the Internet, viewers can imagine the horror of being in the victim's position.

One of the first of these murders to be posted on the Internet was the beheading of American journalist Daniel Pearl by Islamic militants after he had been kidnapped in Pakistan in 2002.

In Iraq, the first hostage to be killed was Italian Fabrizio Quattrocchi, one of four security guards kidnapped in April. He was shot after the Italian government refused to withdraw its 3,000 troops from Iraq. A month later, US engineer Nick Berg was the first hostage in Iraq to be beheaded, with footage showing one of his captors putting a large knife to Mr Berg's neck and cutting off his head.

"It is not just the video broadcast on Al Jazeera which makes an impact, in scaring people away and demonstrating their power to the Iraqi people," says Mr George. "Possibly more effective are the DVD versions which appear 48 hours later in the markets of Baghdad and elsewhere.

"These also show the preliminaries as well as the beheadings, and often include Arabic battle songs and prayers, and apparently these sell extraordinarily well. Other groups saw how effective this was when it was first done with Nick Berg, and they are now copying it."

The US yesterday said it had no plans to release the two Iraqi women it is holding prisoner - Rihab Rashid Taha and Huda Salih Mahdi Ammash, known respectively as Dr Germ and Mrs Anthrax - in contradiction to an earlier claim by the Iraqi administration that they could be freed, and the UK Government said it would not deal with terrorists, despite pleas from Mr Bigley's family.

But the kidnapping tactic has successfully pressured both companies and governments into changing tack. On Tuesday, a Turkish construction company became the latest to halt work in Iraq to secure the release of ten of its staff kidnapped by militants, following at least seven other Turkish companies to pull out after their drivers were seized.

In July, the Philippines withdrew its 51 troops to secure the release of truck driver Angelo de la Cruz, to the fury of the American and Australian governments. President Gloria Arroyo defended her decision on the grounds that there are 1.5 million Filipino workers in the Middle East, and she won the backing of 70 per cent of voters according to polls, but it did not stop the Australian foreign minister likening the Philippines to a marshmallow for capitulating.

"The standard argument is if you give in to their demands on one occasion, they will come up with even more demands," says Mr George.

But for all the public protestations that they will not deal with kidnappers, few Western governments have an unblemished record in this respect, according to David Whittaker, former lecturer in international relations at Teesside University and author of several books on terrorism.

President Carter authorised the sale of arms to Iran to try and secure the freedom of 52 diplomats held hostage in Teheran in 1979, and President Reagan also agreed to sell arms to a state considered the main sponsor of Middle East terrorism in 1985, in exchange for the freedom of US hostages in Lebanon.

The Reagan administration also twice put pressure on Israel to release Palestinian prisoners, in exchange for US hostages held in Beirut and on board a TWA flight hijacked over the Mediterranean Sea.

The British government's only recorded deal with terrorists was the release of hijacker Leila Khaled in 1970, to secure the freedom of 56 hostages, including eight Britons, held hostage when three planes were hijacked by the Popular Front for the Liberation of Palestine.

"Most governments have to say very loudly and very clearly that they will never, ever negotiate with terrorists, but the record is that most governments have in fact done so," Mr Whittaker says.

"It is partly humanitarian instincts, partly political considerations - they have their people back home to face if it all goes wrong - and it may well be that behind the scenes everything is being done to come to some agreement."