N o prizes for identifying the grande dame of Irish theatre, Siobhán McKenna. Reward yourself with a nice cup of tea, however, if you can connect her with the subject of today's edition of the magazine, Roald Dahl.

No? Well, in 1979 McKenna starred in a TV adaptation of Dahl's The Landlady. Aired as part of the BBC's Tales of the Unexpected series, the episode was presented by the great man himself – a rare treat for viewers, and perhaps a tacit acknowledgement of the creepy excellence of both text and film.

The story opens with a young man searching for lodgings in the town where he is to begin a new job. Spotting a “Bed and Breakfast” sign in a window, he peers inside. A dachshund is asleep, curled up in front of a brightly burning fire.

In a few sentences Dahl evokes an inviting, unthreatening environment. As for the eponymous landlady, McKenna inhabits her “round pink face” and “very gentle blue eyes” to perfection, sporting the uniform of harmless old ladies everywhere – flowery dress and lilac cardigan – and deflecting difficult questions from her putative lodger with the deftly-timed offer of a ginger biscuit.

Our photo was taken at McKenna’s own home in Rathgar, more than a decade before she played the Dahl role. It’s an oddly unsettling portrait. No relaxing on the sofa for McKenna: rather, her elegant-but-severe attire and her refusal to acknowledge the presence of the camera suggest a core of steel.

The way she's holding that cup and saucer, however, suggests she may be about to do something unpredictable – just as, in The Landlady, she shifts the tone of the entire piece by suddenly leaning forward to deliver the immortal line: "You have the most beautiful teeth, Mr Weaver . . ."

Clips of this ghoulish little gem can be seen on the internet. But for a shivery seasonal treat, why not get hold of the real thing – a bumper edition of Dahl’s stories – and tuck yourself in? Just don’t blame me if you can’t sleep, ever again.

Arminta Wallace