Although the late Angela Lansbury played a huge variety of roles over the course of her long career, she was perhaps most associated with benign characters, thanks to the enduring Eglantine Price in Bedknobs and Broomsticks and detective Jessica Fletcher in TV series Murder, She Wrote. However, while she rarely portrayed villains, her greatest screen performance is arguably as the atypically merciless, fanatical, and fascinating Eleanor Iselin in John Frankenheimer’s 1962 Cold War conspiracy classic The Manchurian Candidate.

Based on the novel by Richard Condon, the film is a potent blend of paranoid thriller and sharp satire, telling the tale of a returning US Korean war veteran unwittingly brainwashed into becoming an assassin by mysterious Communist forces. Lansbury was completing the 1962 family drama All Fall Down with Frankenheimer when the director offered her the crucial part of the Machiavellian wife of a McCarthyesque politician. Despite being just three years older than her onscreen son Laurence Harvey (and having already been pushed into prematurely-aged roles at 37), she was intrigued and accepted the part, turning egregious Hollywood sexism and ageism into a personal artistic triumph.

We first meet Eleanor Iselin at a military reception for her son Raymond, arriving in Washington to receive a medal for his supposedly distinguished war service. We hear her before we see her, an officious, hectoring voice loudly ordering a General to wait for her arrival. The camera descends from a fluttering Stars and Stripes to reveal Lansbury as she snakes her way through a phalanx of stationary troops, wielding her handbag like a battering ram as she cuts a path to the front. She then expertly sets up a photo opportunity, aggressively shepherding participants and press into her desired positions. Within these few seconds, we are made aware of how formidable a force she is: not just bending the military to her will, but dragging the media and her supposedly-powerful husband, the US senator John Iselin (James Gregory), in her wake, all tacitly endorsed beneath her country’s flag.

With her stiffly coiffured hair, furs, and pearls, Lansbury appears the epitome of a strong, conservative nuclear-family matriarch. She carries herself with a fierce sense of decorum and entitlement, concealing her character’s fearsome ambition beneath a socially-acceptable front of suffocating motherly love.

She skilfully manipulates the stuffily patriarchal world around her with a lethal mix of insults and flattery, knowing just when to bruise and when to soothe fragile male egos. She addresses her son and her husband as her “two little boys,” hissing poison over Raymond’s shoulder until he covers his ears like a child, and easily defusing Senator Iselin’s occasional and usually asinine objections to her schemes.

While John is ostensibly the politician, it is Eleanor who possesses the true skills in this arena, made clear by the scene in which he makes his first anti-Communist allegations. Although she barely says a word during the sequence, Lansbury brilliantly establishes Eleanor’s dominance through her facial expressions, body language, and position within the frame. She stands in the foreground to the side of the screen, watching the television feed of the committee hearing which is happening live in the background.

Her husband awaits her subtle nod before beginning his intervention, and she towers over the TV image as he speaks, a calm and collected Svengali coolly co-ordinating her political puppet show, almost imperceptibly mouthing along to his words like a ventriloquist. She knows just when to stop her blustering husband and make an exit, physically interposing herself between him and the inquisitive Major Marco (Frank Sinatra) under the guise of accidentally getting in their way.

Lansbury’s extraordinary performance reaches its peak with the scene in which she finally explains the conspiracy’s purpose to a seemingly catatonic and compliant Raymond. Essentially a monologue, with George Axelrod’s script requiring her to deliver dense exposition and explain her character’s motivations, it could easily have been overplayed and awkward. Instead, it is utterly spellbinding. Shot low in close-up, her eyes burn with zealous fury, while her uncharacteristically awry hairstyle hints that we are finally seeing the real person behind the performance.

Her calm ferocity is chillingly convincing, her quiet voice thick with ecstatic fervour as she outlines her plans to enter the White House “with powers that will make martial law seem like anarchy!” In a brilliant touch, Lansbury pauses for a moment after this verbal crescendo, and in the silence the small, tight smile of triumph that flits across her face acts as a terrifying punctuation mark to her words. Making her way to the side of her seated son, her hands move insidiously along his chair, uncomfortably tactile and intimate, vehemently reasserting her physical dominion over Raymond to compensate for her loss of his mind. Gradually, her hands move to cup his face as she kisses him passionately on the lips, shielding this final violation from the camera as if even Eleanor can barely bring herself to share the horrifyingly incestuous desires raging beneath her fiercely controlled exterior.

While Eleanor’s icy control appears to have returned for the finale, calmly reassuring her sweating and fidgeting husband as they await the planned assassination of the presidential nominee, the scene ultimately provides the character with her most human moment. In the brief seconds between John’s death and her own, a look of sheer terror and bewilderment crosses her face – the first time we have seen her so completely at a loss. She knows her plans have suddenly failed, and worse, she knows that it is her own tormented son who is about to kill her: her most prized (and abused) possession finally, definitively, defeating her.

It is a testament to Lansbury’s skill and empathy that she gifts a moment of pitiful vulnerability to so despicable a creation. While it seems unlikely that many would argue that Eleanor does not deserve her sorry fate, Lansbury’s remarkable performance ensures that she remains a very human monster – arguably among the most complex, frightening, and believable antagonists ever to grace the screen.