Providing for a nation’s old age is probably the longest-term issue facing any government, So an off-the-cuff comment is not the obvious way to develop pensions policy. David Cameron’s remarks this week about moving public sector workers away from final salary pensions to defined contribution schemes had barely been uttered before his party moved as far away from them as it could. But the UK Tory leader was still right to open up the question.

There is a yawning gap in the UK between public and private sector provision. Many company pension schemes based on an employee’s final salary have been closed or restricted, leaving the individual to bear the risks of what those contributions will buy for retirement. Public sector pensions, meanwhile, can pay up to two-thirds of final salary, with the state bearing the investment and longevity risks.