Fiona Allen is making her Edinburgh Fringe debut next week, more than 20 years after her Channel 4 sketch show Smack The Pony ended.

But her comedy career is a long way from her grandfather’s grim job – as one of the last British hangmen.

In a major interview with The Times today to promote her festival run, the comic was uncharacteristically ‘cautious’ to comment on her ancestor’s profession.

But she did tell journalist Dominic Maxwell ‘they thought they were doing the right thing’ at the time.

Harry Allen and fellow hangman Robert Stewart were the last people to put criminals to death in the UK, executing a pair of murderers in simultaneous executions at different ­prisons in 1964.

The hanging of killer Gwynne Evans was the  29th execution for Allen, who started his career as the deputy of Britain’s most prolific hangman, Albert Pierrepoint.

He also hanged A6 murderer James Hanratty, whose controversial death sentence in 1962 paved the way for the abolition of the capital punishment in the UK.  Major questions were raised over the quality of evidence used to convict him, and his family always protested his innocence. But in 2002 the Court of Appeal found that modern DNA tests proved his guilt.

Publicly Allen said  hanged prisoners ‘die instantly and painlessly’, although private diaries put up for auction in 2008 reveal that one condemned man, child rapist and murderer Peter Griffiths was still alive 30 seconds after the trapdoor opened.

 Allen died in 1992 aged 81,