Are 13 Scouts out to get their Illegal Immigrant badge?

But it seems some of the youngsters at the World Scout Jamboree were prepared for more than just a fortnight of fun.

As thousands from 162 nations enjoyed the activities at Hylands Park in Chelmsford, Essex, 13 of their brethren disappeared.

Nine Scouts from Bangladesh and Uganda never arrived at the campsite, while four from Sri Lanka and Nigeria vanished during the 12-day event.

Police say there are no suspicious circumstances and believe the youngsters may be planning to stay in Britain illegally.

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"They left of their own accord and while some are quite young they appear to be quite prepared and they are primarily in groups," said an Essex Police spokesman.

"It might be they have gone off to see other things in Britain, like going into London rather than being at the Scout jamboree.

"Equally, it might be they are intending not to go back. We cannot rule out the fact they might have come here to start a new life and want to stay.

"The starting point is seeing if they know any people who live in this country and looking into their backgrounds to discover who they might make contact with.

"They are all here legally on official visas, but these are visitors' visas and there will come a point when they run out so we are trying to locate them as quickly as possible.

"We are doing all we can to locate them. It's not unusual to get missing people at this type of event, especially given there were 40,000 people - which is the size of a small town."

The 21st World Scout Jamboree celebrated 100 years of the global Scouting movement, which began when Robert Baden-Powell took 20 boys on a camping trip on Brownsea Island in Dorset in 1907.

Prince William and the Duke of Kent launched the festival on July 27 and the Scouts packed up and went home on Wednesday - apart from the missing 13.

The youngsters are five male Bangladeshis - one is 12, two are 15, one is 16 and the other is 24.

Two girls and two boys from Uganda aged 16 and 17 and a 17-year-old Sri Lankan boy and 15-year-old Nigerian boy have also disappeared.

Also missing are a 15-year-old boy and a 17-year-old girl, whose countries of origin have not been released.

Simon Carter, a spokesman for the Scouting Association, said four slipped away during the jamboree, but the other nine did not arrive at the park.

He added: "Somewhere between the airport and the campsite, they went missing - at which point we have no control over them.

"I don't want to speculate why. We are working with the police.

"The police are saying they do not believe the disappearance was suspicious and it is a police matter.

"Young persons' safety is our priority, but our main security concern was to stop unauthorised people getting in, rather than stopping people getting out. Security is on the inside looking out, not outside looking in."

He added that all Scouts who attended the jamboree had to register their names and addresses and would have travelled to the UK with leaders.

"It's been a fantastic event - 40,000 people had the time of their lives," he added. "It was a multi-cultural melting pot."

Essex Police have circulated names and photographs of some of the missing youngsters to colleagues in other forces to try to track them down.

The Scouts would not be the first to use a high-profile international event as a cover to start a new life in Britain.

At the 2002 Commonwealth Games in Manchester, 21 athletes from Sierra Leone disappeared after the closing ceremony.

And of 58 players from Nigeria and Ghana granted visas to compete in qualifying events for the 2002 Open golf championship, only five actually set foot on the course.