Terrence Hardiman, who has died aged 86, was an actor whose military bearing and deadpan, silently sinister look naturally led him to be cast as authority figures – most memorably as the star of the BBC television children’s drama The Demon Headmaster, in which the description “authoritarian” was more appropriate.
The programme, which began in 1996, was compulsive viewing with its stories of Hardiman’s terrifying megalomaniac exerting hypnotic powers over his pupils. In the opening episode Dinah Glass, an orphan, sits at the head’s desk as he takes off his dark glasses, stares at her with his piercing green eyes and says: “Funny you should be so tired so early in the morning. So tired you can hardly move your arms and legs. You are tired, so tired. You feel your head begin to nod and, slowly, your eyes are starting to close. So tired.”
The popular drama was adapted by Helen Cresswell from Gillian Cross’s early Demon Headmaster books. Two further series ran, in 1996 and 1998, under the titles The Demon Headmaster Strikes Again and The Demon Headmaster Takes Over. Hardiman relished playing the villain, known only as “the headmaster”, who longs to take over the world and starts meddling with evolution after he becomes director of a biogenetic research centre.
When the programme was revived for a new series in 2019, he made a cameo appearance in the last episode – alongside Nicholas Gleaves, who was the new head.
Earlier, as Major Reinhardt in the final series of the second world war drama Secret Army (1979), Hardiman showed subtlety in his portrayal of a German officer dedicated to capturing allied pilots shot down over Belgium and exposing Lifeline, the resistance movement helping them.
Reinhardt, a Luftwaffe major, was a new arrival there, often in conflict with the SS chief Kessler (played by Clifford Rose), and – while yielding results himself – not sharing his superior’s rosy belief in a German victory. The Stage put Hardiman’s portrayal down to “his sharp, melancholy face conveying both the cunning of the hunter and the guilt of the soldier who finds himself terrorising old women and children”. Reinhardt ends up being court martialled and shot.
Later, Hardiman played a less subtle German officer, General Stuckler, a brutal interrogator set on crushing the resistance, in the last series of Wish Me Luck (1990), starring Kate Buffery and Jane Asher in the story of female British agents in Nazi-occupied France.
More benignly, in Cadfael (1994-98), he played Father Radulfus, the abbot and superior of Derek Jacobi’s sleuthing medieval monk.
Hardiman was born in Forest Gate, Essex (now in the London borough of Newham), to Edward Hardiman, a police officer, and his wife, Rose (nee Breeden). On leaving Buckhurst Hill county high school, he studied English at Fitzwilliam College, Cambridge.
He was a budding actor there, along with Jacobi, in the Cambridge University Amateur Dramatic Club – of which he was president – and the Marlowe Society. On graduating, he joined the company at the Old Vic theatre, London (1961-62), making his debut in Doctor Faustus and continuing with what he called “spear-carrying” roles. Then, at the Bristol Old Vic (1962-65), he consolidated his credentials as a classical actor. This was followed by a long run (1966-70) with the Royal Shakespeare Company at Stratford-upon-Avon. He received good reviews for his performances as Mountjoy in Henry V (1966) and Lucio in Measure for Measure (1970), but his standout role was as Mephistophilis in Doctor Faustus (1968), with the critic JC Trewin praising his “haunting” portrayal of “the sad, implacable” character.
Hardiman found wider public recognition when he appeared on TV in Softly Softly: Task Force as Inspector Armstrong during 1971, then over a long run (1972-83) in the ITV daytime drama Crown Court as the barrister Stephen Harvesty.
There were also many one-off character parts, including a member of the Gestapo in Colditz (in 1972) and a Prussian officer in Enemy at the Door (in 1978), before he landed the starring role of Charles Pooter in Basil Boothroyd’s adaptation – in nine 15-minute episodes – of Diary of a Nobody (1979), George and Weedon Grossmith’s 19th-century comic novel. “There’s quite a lot of me in that silly, pompous character,” Hardiman claimed.
Then came his portrayal of the estranged patriarch in My Father’s House (1981), with Judy Holt as the sheltered daughter given fresh confidence by seeing the new life he is enjoying with a glamorous woman. Another starring role came as Chief Superintendent Franks in the tense miniseries Skorpion (1983). Hardiman beautifully played a version of John Le Mesurier’s Dad’s Army character, Sergeant Wilson, in a 1995 episode of the comedy Goodnight Sweetheart featuring a story set in the 1940s.
After making an impact in The Demon Headmaster, he stayed with children’s television briefly to appear on and off as the Grand Wizard Egbert Hellibore in The Worst Witch (1998-2001).
In the 2010 Doctor Who adventure The Beast Below, he played another megalomaniac, Hawthorne, in charge of the government of the Starship UK, carrying the country’s population.
One of his last TV roles was as the prime minister Anthony Eden’s doctor in The Crown in 2017. He had already played prime ministers himself – Ramsay MacDonald in the 1982 film Gandhi and Neville Chamberlain in the Howard Brenton play Never So Good at the National Theatre in 2008.
In 1964, Hardiman married the actor Rowena Cooper while they were both performing with the Bristol Old Vic theatre company. She and their two children, Laurence and Eleanor, survive him.
• Terrence Edward Hardiman, actor, born 6 April 1937; died 18 April 2023