... He could be a tad unpredictable.
Undoubtedly that's why he was so much fun to watch, if a trial for interviewers to control.
Of course for many years he was often drinking heavily. That does tend to contribute to unpredictability, and it may not be especially delightful to deal with, it should be said. O'Toole doesn't seem to have been as obnoxious a lush as some of his fellow "hellraisers," however.