The Princess Royal visited RAF Lyneham yesterday afternoon where she spoke to members of 47 Squadron to show her support.

She is Honorary Air Commodore at the RAF base and was paying a private visit.

"The Princess wished to show her support to the squadron who, this week, has lost a number of their colleagues in Iraq after the crash of a Hercules aircraft there," said a Palace spokesman.

Station commander Group Captain Paul Oborn said: "We greatly appreciate the close relationship we have with our Honorary Air Commodore and value the time she spends with us."

The Princess expressed her condolences to members of 47 Squadron and their engineering support personnel, he said.

In addition, she spoke to staff assisting the bereaved families.

A spokesman for Buckingham Palace said the Queen has sent a message to the families via Defence Secretary Geoff Hoon.

The message reads: "I was saddened to learn of the loss of the RAF Hercules in Iraq on Sunday. I should be grateful if you would convey my deepest sympathy to the families of those who have lost their lives."

The message was signed Elizabeth R.

An investigation into why the Hercules crashed into the Iraqi desert killing all 10 people on board could take weeks.

The marshy terrain and hostile local forces are likely to hamper the painstaking hunt for clues, a Ministry of Defence spokesman said.

He described as speculation reports that they were considering the possibility a bomb may have been on board.

"We are not going to speculate about the causes until we have got a clear picture," the spokesman said.

"Bombs on board, missile strikes, explosions that's a matter for the crash investigators to work through and advise on."

The MoD spokesman said there was "no timescale" for the procedure but made clear it was likely to take longer than a crash probe in the UK.

"This is a marshy area north of Baghdad," he said. "We have got to take into account any hostile forces that might be in the area. It could take weeks."

An Iraqi militant group, Ansar al-Aslam, claimed on a website on Monday that it shot down the aircraft using an anti-tank missile.

A second group of insurgents sent a video to Arabic TV channel al-Jazeera which claimed to show evidence that they brought down the plane.

An MoD spokesman said: "Obviously we will be looking at that carefully but at this stage we can't say one way or the other whether it is what it purports to show."

The relatively slow, low-flying Hercules, renowned for its reliability, came down in clear conditions 25 miles north-west of Baghdad on a routine flight.