The deranged Swinging Sixties comedy that was the making and breaking of David Warner

When Ben Whishaw launched his career with Hamlet at the Old Vic in 2004, theatregoers (and critics) with long memories were driven to compare Whishaw’s performance as a wide-eyed, near-impotent Dane to David Warner’s legendary RSC interpretation of the role in 1965.

As directed by Peter Hall, Warner, who has died at the age of 80, played Hamlet less as a would-be avenger and more as a frightened scarf-clad student, forced into maturity and purpose long before he would ever have wanted. The theatre critic Ronald Bryden said of his performance that he brought "more of humanity into the part than any previous Hamlet I’ve seen", and it remains one of the definitive 20th century interpretations of the role.

Warner, at the age of 24, was lauded as not merely one of the greatest actors of his generation, but someone of near-limitless gifts. It therefore comes as a surprise to look at his career and see that, with a few exceptions, his heyday gave way to a solid but largely unexceptional career as a character actor. He offered intelligence and class in every project that he took on, but he was seldom offered the kind of roles that really gave him a chance to demonstrate his range.

It is perhaps ironic that the part that he may be best known for – as the brutish valet Spicer Lovejoy in Titanic – offered this most sophisticated and intelligent of performers remarkably little to work with, save the opportunity to skulk about looking angry.

Nevertheless, his early work on both stage and screen remains both vital and surprising, whether it was his early performance as Henry VI for the RSC – of which Kenneth Tynan wrote "I have seldom witnessed such a finished performance by an actor who has barely started… I have seen nothing more Christ-like in modern theatre" – or his film performances, which saw him associated with the likes of Terence Stamp, Alan Bates and Albert Finney in the Angry Young Man movement.

His film debut was opposite Finney in Tony Richardson’s Tom Jones in 1963 as the villainous Blifil, in which he demonstrated a fine line in haughty contempt, but he soon made a considerably greater impression in Karel Reisz’s 1966 black comedy Morgan – A Suitable Case for Treatment, which remains his most distinctive film role and a seminal work of its era.

The playwright David Mercer began his career writing naturalistic political drama, but in 1962, he wrote a strange and surreal television film about Morgan Delt, a working-class artist who finds himself adrift amongst the wealthy milieu that he has found himself exposed to thanks to a socially advantageous marriage to a wealthier woman.

Mercer, who suffered from severe depression, was inspired by the philosopher R D Laing, who believed that insanity, rather than something to be terrified of, should instead be embraced, even cherished. His script was initially filmed with the actor Ian Hendry in the title role, to acclaim, but Mercer believed that it deserved greater exposure than its original slot as a Sunday night play for the BBC. It so happened that Reisz, fresh from his success with Finney’s social realist drama Saturday Night and Sunday Morning, agreed with him, and he had just the actor in mind to play Morgan: the man who had just played the definitive Hamlet of his generation.

Without wishing to disrespect Hendry, Warner’s performance as the almost Walter Mitty-like Walter was both electrifyingly thrilling and hilariously funny, and demonstrated that he was an actor of rare and versatile talents. It offered one of Sixties’ cinema’s most iconic images – Warner, dressed in a gorilla suit, speeding away on a motorbike – and, in its presentation of a tortured three-way relationship between Morgan, his upper-class wife Leonie (Vanessa Redgrave) and her bemused admirer Charles (Robert Stephens), offered an ironic and surrealist take on a similar dynamic that Tom Jones’ screenwriter John Osborne had explored in his breakthrough play Look Back In Anger a decade before.

Although the television version and the cinematic film of Morgan were only made four years apart, there was an anger and a verve to the later interpretation that summed up its age brilliantly, shot through with a nihilistic wit that made for thrilling, if challenging, viewing. Warner was never an ingratiating actor, and he was unafraid to play Morgan as a combination of petulant child and idiot savant, whose refusal to obey social norms was both fascinating and – for the characters orbiting him, if not the audience – deeply tiresome.

When he declares that "You can't count on me being civilised – I've lost the thread", it is not so very far from Hamlet baiting Polonius with teasing suggestions of madness. Although, crucially, Morgan ends up institutionalised in a mental hospital, finally finding the innermost peace in confinement that he had failed to find in the hypocritical and superficial world of art.

Warner, bizarrely, did not find the same acclaim as Redgrave for his tour de force performance, although he was nominated for a Bafta (losing to Richard Burton); an award that he never won throughout his long career. It remains a film wholly of its time, a savage take on the Swinging Sixties that is given a bitter wit and irony through the commitment of its lead actor’s performance.

Although he would have been the first to admit that he did not boast matinee idol looks, Warner’s charisma and obvious intelligence as an actor gave the character of Morgan a charm and sympathy that a lesser performer might not have been able to locate; it suggested, along with his Hamlet, that he was on the verge of a glittering career.

That this career did not entirely materialise is hard to explain. Some poor choices of material might be to blame; it was, in retrospect, not a brilliant idea to appear in such forgotten and lightweight vehicles as Peter Hall’s film Work Is A Four Letter Word (opposite Cilla Black) and The Fixer. But he had come to Sam Peckinpah’s attention, and Warner subsequently made three films with the mercurial director, including a pivotal appearance in Peckinpah’s ever-controversial Straw Dogs, and the filmmaker suggested that he was one of his favourite actors.

In between his performances for Peckinpah, Warner was graced with one of the most iconic death scenes in any film, when his photographer character in The Omen was decapitated by a pane of glass. Perhaps appropriately, the prop head of his character ended up being given to his ex-wife Sheilah Kent in a divorce settlement.

Warner’s saturnine looks made him a natural fit for villainous characters as he advanced into middle age, sometimes memorably – as in his Jack the Ripper, opposite Malcolm McDowell’s HG Wells, in 1979’s Time After Time, or his dastardly Evil in Terry Gilliam’s 1981 Time Bandits – or in less distinguished projects, such as his mad scientist in Teenage Mutant Ninja Turtles II: The Secret of the Ooze.

Like many actors of his generation, Warner moved to Hollywood and took a drily unfussy attitude to his career, adding class to undistinguished projects and, when he was given a good role (such as his Heydrich in 1978’s TV film Holocaust), making the most of it with a flair that reminded viewers with long memories of what a distinguished and exciting performer he had been when he had emerged in the Sixties.

He left the stage for a long time after an attack of stage fright while appearing in I, Claudius in the early Seventies, but returned later in life with fine and distinguished performances as King Lear, Falstaff and Andrew Undershaft in Bernard Shaw’s Major Barbara.

It is tempting to suggest that he derived more professional satisfaction – if, inevitably, smaller paycheques – from such appearances than he did from cameos in the likes of Mary Poppins Returns and Star Trek VI: The Undiscovered Country, but Warner took an unpretentious attitude towards his work. He was often at his best, especially later in life, in comic roles, such as a ripely self-parodying 2015 appearance in an episode of Inside No 9, in which he slyly ribbed his natural sternness as a ferocious but prurient magistrate overseeing a witch trial.

Warner, who was a notably kind and unpretentious man in private life, often ran the risk of being underappreciated. But anyone who can see the vitality that shines out from his earliest roles – not least Morgan – should recognise that this brilliant actor deserves to be remembered as one of the most exhilaratingly gifted performers of his generation.