Peter O’Toole took the sizzling secret illicit affair he had with the legendary Elizabeth Taylor to his grave, guarding the news of their steamy relationship to the end.

“Peter had long harbored lust for Liz,” a source told The National Enquirer about the late actor, who passed away over the weekend at age 81, and his on-screen leading lady, who died in 2011 at the age of 79 of congestive heart failure.

“There was always a friendly compe­tition between Peter and Richard Burton,” said the source about her late husband who passed away in 1984.

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