A swaggering romantic
"Lawrence of Arabia" established him as a major screen actor. But living down his performance in the epic film became somewhat of a problem, and for most of the 1970s O'Toole found he was playing nothing but the swaggering romantic lead.
In 1980, he made a humiliating return to the Shakespearean stage in London after a 20-year absence.
O'Toole's blood-soaked Macbeth at the Old Vic theater provoked outright laughter from the audience and made front-page news for its sheer awfulness.
For the next few years, O'Toole found it difficult to be taken seriously as a stage actor.
Making a comeback in the 1980s, he also gave up drinking. Years of abdominal pain and almost continuous consumption of alcohol had led to a diagnosis of pancreatitis and a warning that liquor would soon kill him.
A supporting role as the kindly but bemused English teacher in Bernardo Bertolucci's 1987 Oscar-winning film "The Last Emperor" showed the public a new side to the hell-raiser they had come to expect.
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A year later, at the age of 56, he won rave reviews for playing his old Soho drinking pal in the play "Jeffrey Bernard is Unwell" in a part that seemed to mirror his own misfortunes.
He had announced he was retiring only last year.
"It is time for me to chuck in the sponge. To retire from films and stage. The heart for it has gone out of me: it won't come back," O'Toole said in a statement.
"It's my belief that one should decide for oneself when it is time to end one's stay."
Michael Higgins, the president of Ireland, was one of the first to react to his death.
"Those who saw him play leading roles on the screen from Lawrence in 1962, or through the role of Henry II in Becket, and The Lion in Winter, or through the dozens of films, will recognize a lifetime devoted to the art form of the camera," Higgins said in a statement.
British Prime Minister David Cameron said in a tweet that "Lawrence of Arabia" was his favorite film, hailing O'Toole's performance in it as "stunning."
Daughter Kate O'Toole thanked the public for what she described as an outpouring of love for the late actor.
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She asked for her family to be allowed to grieve in private, saying in the same statement it would organize a memorial service "filled with song and good cheer" in due course.
O'Toole leaves behind children Kate and Patricia from his failed marriage with Welsh actress Sian Phillips, and Lorcan, his son from a relationship with Karen Brown, a former girlfriend.