Prime Minister David Cameron promised voters last year that his Conservatives would be the true working-people’s party in Britain. Try telling that to the Welsh steel workers at Port Talbot whom Mr. Cameron’s green-energy policies are about to push out of their jobs.

The latest blow to Britain’s steel industry comes as India’s Tata Steel said this week it will try to sell its U.K. operations. Tata is clocking losses that may be as high as £1 million ($1.4 million) a day, and now says it has more or less written off the value...