More than half of fixed speed cameras in England and Wales do not work at any one time, according to Which?, the consumer watchdog.

A study found that the chances of being caught speeding vary dramatically from county to county, with all 60 Sussex cameras in operation while just 10 per cent of Lancashire's 287 sites are ready to snap motorists.

Less than 47 per cent of all fixed cameras are operational at any one time, Which? said, with most areas having more yellow boxes than actual cameras.

Durham said it used a single mobile camera with no fixed sites. Police authorities in Dorset, Hertfordshire, Merseyside, Norfolk and Suffolk refused to provide data.

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