Leigh Day & Co is not a firm looking for the quiet life. And if a case is out of the ordinary, the London-based practice is almost guaranteed to consider taking it on.

However, one of the drawbacks of handling such cases is that the success rate can be lower than that of other firms which prefer to concentrate on more straightforward matters.

Martyn Day, joint founding partner with Sarah Leigh of the nearly 30-strong firm, recalls that he only lost about two or three cases over a 10-year period in his previous personal injury practice.

Today the risk of defeat is greater, but the satisfaction of success is also higher.

A recent fight to ban traffic from a busy London road during times of high air pollution typifies the sort of case the 10-strong Leigh Day environmental issues team turns its hand to. And although rejected by one of the senior judges of the Queen's Bench Division, Mr Justice Macpherson, who suggested that moving home was the answer to escaping London pollution, the firm has not dropped the fight.

Appeal moves are now under way and if successful the victory will have implications for authorities throughout the UK, not just in the capital.

The case was brought by parents in the London Borough of Greenwich on behalf of their children who suffer from asthma. They sought judicial review of the council's refusal to impose traffic bans on Trafalgar Road during times of high pollution under the 1984 Road Traffic Regulation Act.

On behalf of the parents, counsel Graham Read argued that the Act allowed traffic to be restricted or prohibited in circumstances where there was a likelihood of danger to the public.

After examining the Act, Day took the view that its interpretation should entitle the parents to call for closure during times of high pollution to save their children from "likely danger" which he viewed as being caused by the road in the eyes of the law.

He still believes that argument is correct and thinks the chances of an Appeal Court reversal of the High Court ruling are good.

"We feel we have a good chance of having the High Court ruling over-turned by the Appeal Court and are hoping for an early hearing," he said.

"There is a danger to the public from use of this road, and on our reading of the Act the local authority has the power to close it and should use that power when necessary."

Other Leigh Day cases have included battles over the effects of electro-magnetism on people who live near high voltage power lines, on behalf of leukaemia victims from the Sellafield area, challenges over coastal pollution, plus actions on behalf of people suing tobacco companies over the harmful effects of smoking.