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The lawyers who took on the big US tobacco companies, and won, have now set their sights on the food industry. Newsnight’s science editor, Susan Watts, asks one of them why he has chosen this particular fight.

Don Barrett likes his opponents powerful, and rich. He is the lawyer whose decade-long battle to force the tobacco companies to admit they knew cigarettes were addictive and pay the medical costs of victims was depicted in the film The Insider.

He and his colleagues eventually forced a settlement that cost the industry more than $200bn (124bn). The lawsuits made Mr Barrett a very wealthy man. But he says it is not the potential for another big pay-out that is now making him target “big food”.

“I’m 68 years old, frankly I don’t need the cash, the law’s been good to me,” he explains. “This is my job, but here we have an opportunity to really help people. We’re not saying the food industry is the same as the tobacco industry that kills 500,000 Americans a year, but we are saying there is an epidemic of obesity that is affecting the overall health of the American people.”

Mr Barrett is one of more than a dozen lawyers who has filed cases against some of the US food industry’s biggest players.

They are not the first lawsuits to target food manufacturers. For nearly a decade, US lawyers have pursued a variety of approaches to try to persuade fast food chains to produce healthier, more nutritious food, but these are being seen as some of the most aggressive, despite the simplicity of their approach.