"The one place where we do have leverage with them is on the tax they pay. They’ve also had a massive corporation tax bonus because corporation tax on a lot of these contracts [when they] were signed...was around 30 per cent. Under this government it has now dropped to 17 per cent. So we are estimating that some of them have saved around £190m in corporation tax payments alone. That is money that is owed to our public sector, and is money we could get back with a windfall tax."