What made Peter O'Toole such a mesmerizing presence on the stage and screen?

The Irish-born O'Toole, dead at 81 on Sunday, had more than good looks and a rakish charm going for him. He was the consumate professional actor, able to elevate a production far beyond the ordinary to make it unforgettable. To his craft, he brought unbending dedication and a an attention to detail bordering on the obsessive.

Here's how he prepared for his greatest role, that of T.E. Lawrence in David Lean's epic Lawrence of Arabia:

At six feet two, Mr. O'Toole was not an obvious choice for the role of a five-foot-four scholar-soldier, and the producer, Sam Spiegel, had found him bumptious in a meeting. But after Marlon Brando turned down the role, Lean lobbied for Mr. O'Toole and won the day.

His casting led to a mesmeric yet meticulous performance that brought world renown and an Oscar nomination to an actor whose only notable screen appearance to date had been as a priggish young officer in "The Day They Robbed the Bank of England" in 1960.

Whatever his later reputation as a roisterer, Mr. O'Toole was conscientious when it came to preparing for a role. In the two-odd years it took to shoot "Lawrence," he read all he could about the man, studied Bedouin culture, lived in a Bedouin tent, taught himself the essentials of Arabic and learned to ride a camel. His acting method, he wrote in his autobiography, was a process that blended "magic" with "sweat," a matter of allowing a text to flow into his mind and body until he fully inhabited the character - "that simple, that difficult."

Mr. O'Toole admitted to being "a very physical actor."

"I use everything - toes, teeth, ears, everything," he said.

He disdained the "method" acting of Stanislavsky popular with American actors like Marlon Brando and James Dean, preferring a more "naturalistic" approach by immersing himself so thoroughly in a character that the personality and quirks of a real person would emerge. It led to some critics accusing him of overacting:

Mr. O'Toole threw himself wholeheartedly into what he called "bravura acting," courting and sometimes deserving the accusation that he became over-theatrical, mannered, even hammy. His lanky, loose-jointed build; his eyes; his long, lantern-jawed face; his oddly languorous sexual charm; and the eccentric loops and whoops of his voice tended to reinforce the impression of power and extravagance.

Burton called him "the most original actor to come out of Britain since the war," with "something odd, mystical and deeply disturbing" in his work.

Some critics called him the next Laurence Olivier. As a young actor, Mr. O'Toole displayed an authority that the critic Kenneth Tynan said "may presage greatness." In 1958, the director Peter Hall called Mr. O'Toole's Hamlet in a London production "electrifying" and "unendurably exciting" - a display of "animal magnetism and danger which proclaimed the real thing."

O'Toole always played it close to the edge, as in his portrayal of King Henry II in the film adaptation of James Goldman's Broadway hit Lion in Winter. Along with a very young Anthony Hopkins (Richard), a teenage Timothy Dalton (King Phillip II of France), and Katherine Hepburn's Eleanor of Aquitaine, O'Toole chewed the scenery with gusto in a marvelous and effective piece of "bravura" acting. Lesser talents would no doubt have gone over the top. But O'Toole's controlled fury and charismatic embrace of the largeness of Henry's character, brought him one of his 8 Oscar nominations.

Many critics consider him to be the finest English speaking actor of his generation. Considering his immense body of work on stage and screen, it's hard to argue with that notion.