Two of the world’s biggest tobacco companies are to ask the high court in London on Wednesday to strike out a case against them alleging the exploitation of Malawian farmers and their children as a result of their drive for profits. British American Tobacco and Imperial Brands, both based in the UK, deny the allegations. They are asking that the case be dismissed on the grounds that lawyers for the farming families cannot prove the tobacco they grew ended up in their cigarettes and other products.