Retiring (or already retired) before 2016? Expect to live a long time? You probably won't see investment returns beat state pension deferral.
Until April 2016, pensioners who delay taking their state pension get a generous 10.4 per cent boost to state pension for every year deferred. So you only have to live for 9 years to benefit from the decision.
The rate is twice what you can expect in returns from investing in equities - and is guaranteed by the government. It might be an attractive proposition for someone in good health with substantial private savings to replace the state pension for the years they defer or who is willing to carry on working.