British anti-war protesters have set off from London for Baghdad in a convoy of buses.

They say they want to act as "human shields" against any attack on Iraq.

Travelling in a double decker bus and two London cabs about 50 volunteers left on Saturday.

The activists, who range from a 19-year-old factory worker to a 60-year-old former diplomat, said they expected hundreds, possibly thousands, of people to join them en route.

In a separate peace effort, veteran Labour politician Tony Benn will fly to the Iraqi capital next week to try to meet Saddam Hussein.

They are not a faceless mass who don't matter if they die Campaigner Grace Trevett

"The purpose is to explore the prospects for peace," the former Cabinet minister said.

"We hear President Bush and Tony Blair every day but we don't hear from Saddam Hussein.

"It is a good sign that he may be willing to meet me."

Among the 50 "human shield" protesters is veteran peace campaigner Grace Trevett, from Stroud in Gloucestershire.

Ms Trevett and her fellow campaigners say they are willing to put themselves in the firing line should US and British forces bomb Iraq.

Five-year-old Stuart Lockwood was used as an involuntary human shield in 1991

They plan to identify potential bombing targets such as power stations and bridges and act as human shields to protect them.

"For me there are big questions over whether an invasion is necessary," Ms Trevett said.

"I was in the US in April to take part in a peace march, but while I was there the people of Iraq were being demonised and their children were said to be spies.

"I believe human beings are equally precious, equally important wherever they come from.

"They are not a faceless mass who don't matter if they die."

The whole point of being a human shield is that we can change public and world opinion Campaigner Ube Evans

The group will collect aid for the Iraqi people on their 3,000-mile journey before setting themselves up at key installations in Baghdad.

A second convoy is planning to leave on 15 February, when up to 600 people are expected to fill a further six double-decker buses.

Stage handler Ube Evans, 50, originally from Hay-on-Wye, who is also leaving with the convoy, said: "Somebody's got to save humanity from themselves. I'm very scared.

"The whole point of being a human shield is that we can change public and world opinion."

The US has warned Iraq that using human shields is a war crime and that it would not stop specific sites from being attacked.

During the 1991 Gulf War, Saddam Hussein was accused of detaining Iraqi and Kuwaiti civilians at key military and industrial sites in Iraq.