Security concerns for British workers in Iraq have increased with the kidnapping of British-born charity worker Margaret Hassan.
Concerns for Britons' safety are growing - but how many are in Iraq?
It has been estimated that about 2,300 UK civilians are working in Iraq - as aid workers, missionaries or private security contractors, for the government, or in other private firms.
But one of the most striking things about the flow of UK workers to Iraq is that nobody is sure exactly how many people are there, who they are, or what they are doing.
Government organisation UK Trade and Investment says about 60 British companies are operating in Iraq.
But such is the instability of the country that many companies are reluctant to publicise their presence.
Moreover, the agency has no idea how many employees work for the companies, as many do not register, believing it to be safer.
It is now advising firms against "all but essential travel to Iraq" in the light of the heightened kidnap threat to Westerners.
British engineer Ken Bigley was executed by hostage-takers after three weeks in captivity.
And Mrs Hassan, who has dual British-Iraqi citizenship, has been seized on her way to work as head of charity Care International's office in Iraq.
A UK Trade and Investment spokesman said: "I would urge all British nationals in Iraq to consider whether their presence in Iraq is essential at the moment. The security situation is dangerous.
"They should also as a matter of urgency review their own security arrangements and make sure they are adequate.
"I'm not aware of companies pulling out of Iraq but the threat to British nationals remains high, that's quite apparent."
He was unable to give specific details of firms currently in Iraq but said they were carrying out contracts totalling about £1.4bn.
The companies, many of them large, are involved in all sectors associated with reconstruction of the country's infrastructure, ranging from security to water and electricity.
"I can't even say how many British people are out there as they don't register," he told the BBC.
"Some companies believe that telling people you are out there in Iraq is a bad thing."
However, he said it was in their interests to register because the authorities would then know who was where if things went wrong.
Mr Bigley and his American colleagues Jack Hensley and Eugene Armstrong were taken from their Baghdad home on 16 September by the Tawhid and Jihad group.
They had been working for Middle East-based general services and construction contractor Gulf Supplies and Commercial Services.
The UK Trade and Investment spokesman urged firms and individuals to consult the Foreign Office before heading for Iraq.
The Foreign Office tells companies they should "only consider visiting Iraq if you have strong commercial or professional reasons to do so".
Following Mr Bigley's murder, the Foreign Office warned of a "direct threat of kidnap" in parts of Iraq.
Security arrangements should be reviewed immediately, it said, and if they are not adequate then people should "leave Iraq immediately".
The Foreign Office said 12 Britons had been killed in terrorist incidents in Iraq since March 2004, and many more seriously injured.
However, the chief executive of the British Consultants and Construction Bureau, Graham Hand, said there was no sign of UK companies quitting Iraq as a result of the kidnappings.
"Obviously everybody is extremely cautious," he said.
"I don't think there would be any hesitation in pulling out if they felt it was necessary but at the moment everybody is sitting tight.
"We are dealing with very serious people here who are not in the business of cutting and running if they have undertaken to do a job."
He said the dozen or so consultancy firms he dealt with would now be concentrating on protecting their staff.
"That is going to involve armed British guards at all times, escort vehicles bristling with armed guards.
"It's just about possible to work with that level of protection but it's not easy."