The sign at the exit to Baghdad’s green zone reads: “You Are Now Departing the International Zone. Attention, Stop Here and Load Weapon.”

This is the transition point between the relative safety of the heavily protected enclave and the “red zone” of the real Baghdad.

Yesterday Deborah Haynes, the new Baghdad correspondent for The Times, and I wanted to move from one high-security Baghdad base to another to see Iraqi and Western officials working together. Such a transfer is entirely dependent on security guards such as those who were abducted yesterday.

The day did not begin well, the green-zone Tannoy blaring “Incoming, incoming, incoming”, to signal mortar rounds.

Minutes later we were in flak jackets and helmets inside a bulletproof car and whizzing through the streets, surrounded by our temporary detail of crop-haired British guards armed with machineguns, pistols and a Batbelt of protective and offensive weapons peeking out between Kevlar and tattoo.

Throughout the drive, trained heads swivelled and radios crackled as we raced along bomb-scarred roads and past the blackened carcasses of cars unluckier than ours.

For long periods we were stuck in traffic alongside Iraqi drivers – any of whom could have been a suicide bomber – but who in truth were as nervous of us as we were of them.

Whenever we could we by-passed traffic jams, bouncing up on kerbs, across central reservations and through Iraqi and American checkpoints, leaving Iraqis frying in our wake.

Our guards were infallibly courteous, good-humoured and professional. But theirs is a different world. When I thanked the team leader for helping us do a good day’s work he shrugged and smiled: “Any day you go out and come back is a good day.” These men are part of an army of about 10,000 former soldiers and special forces personnel who provide contract bodyguard services for up to $1,000 (£500) a day.

The Americans and British, as well as Iraqi firms, have won most of the contracts.

A past career in the British SAS or SBS (Special Boat Service) or their American equivalents, Delta Force, Rangers, Green Berets and US Navy Seals, is the best curriculum vitae.

The companies with the most lucrative contracts include the American Blackwater, which among other duties guards US diplomats in Iraq, and the British Aegis Defence Services run by Tim Spicer, a former lieutenant-colonel in the Scots Guards.

His company won a $360-million Pentagon contract for three years to provide security and coordination between the US military and construction firms, and is about to extend this for another two years at a cost of $490 million.

Sources with long experience of working as bodyguards in Iraq say that the work is now infinitely more dangerous than it was a few years ago.

The pop-star salaries originally on offer have also settled down, with the majority of contract workers now on annual salaries rather than short-term payments.

The majority of bodyguards are on annual salaries of about $150,000 – the equivalent of about $430 a day. Those with top-level management roles are on higher salaries, about $250,000 a year.

Numerous private security contractors have lost their lives. Blackwater had four of its employees killed and mutilated in the town of Fallujah in 2004.

“As the latest kidnaps have proved, it is very difficult to know how to react when you are confronted by what seems to be a legitimate body of Iraqi paramilitary police officers, only to discover they are insurgents dressed up in stolen uniforms,” a British security company source said.

Thirty-eight British contractors have been killed in Iraq since the start of the war, according to the Iraq coalition casualty count.

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