My father retired from the RN aged 53, and took another job for seven years, retiring from that aged 60. He got a call from the Home Office soon afterwards, asking if he'd like to apply to join the Police Complaints Authority, for three days a week. The same pension issues as described above came up, so he told them where to put it.
Just as with QFIs, HMG lost a good employee by the tried and trusted shot to the foot