In a trade dominated by egotists, the actor Rex Harrison, whose centenary will be celebrated by the Museum of Modern Art beginning tomorrow in a month-long series of his films, was among the most self-obsessed. I met him while conducting research for a biography of Carol Reed, the British director of such cinema masterpieces as “The Third Man.”

Harrison (1908–90) offered a unique dimension to understanding the elusive Reed. He had worked with Reed both in the 1930s, before the young director had made his most accomplished films, and in the ’60s, when Reed was past his prime. I met Harrison for tea at the Ritz in London and he proved courteous, humorous, and full of stories that tellingly compared the younger and the older Reed.

But Harrison’s flashes of ego were the most memorable aspect of our meeting. In 1961, he was cast by Reed as Pope Julius in “The Agony and the Ecstasy,” from Irving Stone’s popular biography of Michelangelo. Much of the action was filmed on a set posing as the Sistine Chapel, where Charlton Heston lay on his back for weeks affecting to paint the ceiling.

Harrison’s understanding of events was typically self-centered. “The film is about a pope who commissions a ceiling,” he told me, without any of the self-deprecating flashes that might, to a fellow Englishman, have mitigated his insufferable arrogance. It was one reason that, when I turned in my Reed typescript and Harrison died shortly afterward, I demurred when asked to write his biography.

As I made my excuses to my publisher and agent, I found I was talking myself into taking the commission. As an actor, Harrison was a technical genius. His effortless delivery of difficult prose, both onstage and in front of a movie camera, kept him in work for the whole of his life and provided us indispensable performances in films such as “Cleopatra” (1963) and “My Fair Lady” (1964), for which he won the Academy Award for Best Actor.

Harrison made little conspicuous effort to act — he was inescapably Rex in everything — but his understanding of the text meant that he hit every note the first time. He was silver-tongued and an eager womanizer, two qualities that allowed him to prosper in the treacherous jungles of Hollywood.

Harrison was a cad of the first order. His black-hole egotism meant he could not appreciate the worth of others, particularly other men, and his attitude to his string of wives (six in all) and lovers was often hard and heartless. I concluded that he was not someone with whom I could spend the many thousands of hours a book takes to write.

A life of Harrison would be not merely a show business biography but, like that of Henry VIII, an account of the lives of his wonderful wives. I remember describing how the book would almost write itself if one were to give a chapter to each wife and set them against the life of the old priapic bounder.

I eventually agreed to write Harrison’s life. As expected, Sir Rex (he was knighted in 1989) turned out to be every bit the spoiled, mollycoddled, slick, smug, insensitive, shallow actor I was expecting. Each one of his wives, though, was exceptional, starting with his short-lived first bride, the fashion model Collette Thomas (whom he married in 1934), and then the actress Lilli Palmer (in 1943), a Jewish refugee from Nazism who followed him to America.

In Hollywood, Harrison began an affair with the blond starlet Carole Landis. One night, after she pressed him to leave Palmer and marry her, he left her in such distress that she killed herself. His studio hushed up the scandal, but Harrison was obliged to retreat back to Britain, and the film he was completing at the time, aptly called “Unfaithfully Yours,” languished for years before it could be released, such was the anxiety about public reaction to the suicide.

Next in line to become Mrs. Rex Harrison, in 1957, was Kay Kendall, a beautiful and talented British actress who is still remembered for her elfin looks and endless vivacity. Kendall died of leukemia in 1959, and Harrison, for once, behaved well, nursing her to the last. But all credit he may have accumulated for doing right by Kendall was quickly spent as he took on the tempestuous Welsh actress Rachel Roberts, in 1962.

Roberts and Harrison made a formidable pair. Both were hugely talented actors, both enjoyed getting blind drunk on a daily basis, and both were prepared to wage their corrosive domestic battles in public. At one time in Hollywood in the 1960s, no party was complete until the Harrisons had arrived drunk, fought each other like cats in a sack, then stormed off into the night in pursuit of more drink and high drama.

After Roberts came Elizabeth Rees, 28 years Harrison’s junior and former wife to the rumbustious Irish actor Richard Harris. Harrison despised Harris and resented his success as a singer, notably of Jim Webb’s epic “Macarthur Park,” which overshadowed Harrison’s talking in tune in “My Fair Lady.” Elizabeth was soon miserably unhappy, incarcerated in their grand home in Belgravia, London, where he opened her mail and threw away letters and invitations from her friends.

Harrison’s last wife, Mercia Tinker (in 1978), had nothing to do with the stage, with movies, or with show business. She suffered Harrison’s unending vanity with dignity and ensured that his last years were comfortable and companionable.

Starting tomorrow, MoMA will show 11 of Harrison’s films, including those mentioned above. In each, Harrison displays a crispness of delivery and a conviction of character that typifies English drawing-room stage comedy acting at its best. For all his personal excesses, the films he leaves behind show a dedicated actor at the top of his game.

Through March 24 (11 W. 53rd St., between Fifth and Sixth avenues, 212-708-9400).