The crew of the aircraft carrier Ark Royal have begun their voyage to the Gulf as part of the biggest British naval deployment for two decades.

The 20,000-ton flagship began leaving Portsmouth at 1230 GMT with a total crew on board of 1,100.

Officially the crew are heading for Malaysia to take part in joint exercises in June, in a voyage which will last at least six months.

But they could be used in any action against Iraq "if and as required", the government has said.

The troops were seen off by hundreds of relatives and other supporters, cheering and waving to show their support.

Susannah Black, whose 29-year-old boyfriend Lieutenant Richard Webster was on board, said she had "mixed feelings" about saying goodbye to him and was "trying not to cry".

The 1,100 troops on board waved as they left

"He'll be excited about the trip, he's on board a new ship, but I'm not sure what the future's going to bring - the next few months.

"But he's a tough boy. I'm sure he'll grab the situation with both hands and do his job to the best of his ability."

The ship will be joined in coming days by 15 surface vessels - including a frigate, a destroyer and two support vessels - and a submarine which can fire Tomahawk cruise missiles.

In total, the number of UK troops in the Gulf region will reach 8,000 - 5,000 Royal Navy personnel and 3,000 Royal Marines.

Captain Alan Massey, commanding officer of the Ark Royal, described the mood on board as a mixture of excitement and nervousness.

Susannah Black, whose boyfriend is on board, has "mixed feelings"

Lieutenant Colonel Ben Curry, headquarters spokesman for the Royal Marines, said the crew were "chomping at the bit".

Liverpudlian Angela Scales, 18, a radar maintainer, and the youngest crew member on board, said: "Obviously you are aware of what is going on but no-one knows what is really going to happen and we could be back home in a few months.

"It is my first time at sea but I am not nervous."

The ship, after heading to Scotland to pick up supplies, will meet up with the others in the Mediterranean in a fortnight and await orders.

BBC defence correspondent Paul Adams, in Portsmouth, said that if it did come to action against Iraq, the Ark Royal would probably lead an amphibious assault on the south of the country.

But he said the troops may have to await orders in the Mediterranean for some time yet, and it could be well into February before the task force reaches the Gulf.

This is about getting the military hardware and the men in place for a war which most people believe is going to happen The BBC's Paul Adams

He said the number of UK troops in the region, although "significant", was "absolutely dwarfed" by the number of US troops being sent out in a "relentless ratcheting up of the pressure on Iraq".

"I get the feeling we are getting to the point now where the military build-up is getting beyond the point of no return," he said.

"This is not simply about sending messages to Saddam Hussein any more - this is about getting the military hardware and the men in place for a war which most people believe is going to happen."