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".
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Not a bad day at all - just a little patchy rain in the far north of Scotland.