Thieves up and down the country are exporting the stolen luxury sports cars, worth between £60,000 and £90,000 each, to Africa, the Middle East and Malaysia, where they fetch two or three times their retail price in the UK.

Already the international black market has cost Britain's biggest motor insurer, Norwich Union, £2.1 million in Mercedes claims in less than two years.

Now the insurer is warning drivers to be on their guard - and to ensure they fit their pride and joy with the best security devices possible to foil villains who 'steal to order'.

Richard Cole, Norwich Union's motor marketing manager, said: "We're talking about professional thieves who are highly sophisticated.

"More often than not these thieves are stealing to order, and when they target a car it's rarely recovered.

"This is a lucrative trade. Scotland Yard has warned us about the rise in these types of thefts and our own research confirms their fears. That's why we're warning drivers to beware."

Norwich Union is now asking Mercedes SL car drivers to fit Thatcham Category 1 security devices. Thatcham Category 1 is a security device that is fitted to most vehicles manufactured since 1996.

Mr Cole added: "We know that a Thatcham Category 1 security system almost totally eradicates the risk of a car being stolen, and we're encouraging Mercedes drivers to fit them to prevent their cars vanishing abroad."

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