In a previously unseen essay published yesterday, the writer described beards as “hairy smokescreens behind which to hide”.

The author of classic stories such as Charlie And The Chocolate Factory and James And The Giant Peach would clearly have bristled at the facial hair sported by Take That frontman Gary Barlow and new Labour leader Jeremy Corbyn.

He should accept it as it is and should peer into the mirror only once a day, when shaving

He wrote: “The whole business is disgusting. I have always felt that unless a man has a sound medical reason for doing so, then the cultivation of a beard is nothing more than a studied and reprehensible act of vanity. A man is not meant to look beautiful. He should not even be thinking about his face. He should accept it as it is and should peer into the mirror only once a day, when shaving.”

The Cardiff-born author also expressed concerns about the time needed to wash dirt and food from beards every morning.

Dahl, who died from a blood disease aged 74 in Oxford in 1990, also shared his strong views about nasty teachers and gluttonous children during his lifetime.

One of his 17 children’s stories, The Twits, featured a particularly unappealing bearded character.

Mr Twit, portrayed by Jason Watkins in a play at London’s Royal Court Theatre, had a horrible, dirty beard that he never washed “even on Sundays”.