By Mikey Smith Ministers have backed down in a row over cash for a northern airport, in a glimmer of hope for campaigners. Before Christmas, Transport Secretary Mark Harper initially blocked plans to divert cash intended to build a cancelled rail project to help reopen Doncaster Sheffield Airport. But in a letter seen by this newspaper, the top Tory did not rule out allowing the transfer of funds to go ahead. Local Labour leaders have been working to revive the scuppered Doncaster Sheffield Airport, providing transport in the north a much-needed boost after Rishi Sunak’s scrapping of HS2. They…