When old age pensions were introduced in 1909, claimants had to be 70 years old. Life expectancy was 50 at the time.
With people now living, typically, into their mid-80s, an equivalent policy would mean that the state pension would only begin once you had celebrated your 100th birthday.
Source: Mark Littlewood, director-general of the Institute of Economic Affairs, The Times, 16th May 2013.