Sorry, poached swan's off: Calls for clampdown on river bandits from eastern Europe

Except, that is, when it is being chased by a gang of hungry, knife-wielding Eastern Europeans.

Polish and Lithuanian immigrants have been seen trying to drag the 20lb birds away, while the remains of some have been found butchered on the towpath near Leighton Buzzard in Bedfordshire. Hundreds are believed to have disappeared from the area.

Now, just in case the newcomers are unaware of the law protecting swans, members of Luton Angling Club have come up with a sign making it clear that they are not for human consumption.

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They hope British Waterways will erect it along the canal, along with similar notices featuring carp.

The custom of feasting on roast swan died out in Britain a century ago and killing wild swans - which officially belong to the Queen - is now punishable by six months in jail and a £5,000 fine.

Club official Joanne Edwards, 44, who patrols the canal regularly, described a number of tense confrontations with Poles and Lithuanians.

"Every time I try to explain to them that they can't treat our waters as a larder they just pretend they don't understand," she said.

"On one occasion there were four of them fishing and they'd already taken a fish without putting it back.

"Then they got a swan round the neck and pulled it back up on to the bank and the four of them were fighting with it, but luckily it was strong enough to pull away."

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Miss Edwards, 44, from Dunstable, added: "A few years ago there were lots of swans on every section of the canal. I recently patrolled a six-mile stretch and saw just two. They're virtually gone from quieter stretches.

"Even the number of ducks seems to be less. It's dismal, and the police and Environment Agency don't seem to want to react."

She added that the migrants had failed to grasp the concept of catching fish for sport and returning them to the water.

"They think they can catch the fish for food, but the club leases the fishing rights on this stretch and our rules are clear that all fish caught must be put back.

"We first noticed the problem two or three years ago. Now the carp have nearly all gone. You're lucky to catch one at all in this canal."