The Prince of Wales joked he was "very grateful indeed for the perfectly kind wishes about my rather slowly-approaching grandfatherhood".
Charles said during a visit to West Yorkshire, "Some of you may have realised that with grandfatherhood comes, in four months' time, old age pensionerhood".
The Prince added that he hoped he had "a long shelf-life".
Warning: This video contains flash photography:
More top news
Saudi Arabia will allow cinemas to open from next year for the first time in more than 35 years.
Two people have been injured in a house explosion this morning.