So the 29-year-old Miss Zeta Jones clearly likes her leading men on the grizzled side, while the grainy photographs from a Spanish beach which graced the tabloids last week suggest Mr Douglas has lost none of his enthusiasm for the younger model. Is this just a summer fling? A friend of his latest squeeze is reported as saying: "Catherine likes Michael. But she doesn't want anything too serious at the moment."
Which is perhaps just as well. Michael Douglas is a man whose love life has never lacked either variety or frequent changes of scenery. Until recently he had been linked with Maureen Dowd, star Washington columnist for the New York Times. As his former wife Diandra noted with exasperation before throwing in the towel two years ago: "The other women were difficult to deal with."
And difficult to keep count of. There are so many notches on the Douglas bedpost that it must now resemble a carpenter's workbench. Indeed his fame as an actor and producer is only matched by his reputation as a serial swordsman. "Sex is a wave that just sweeps over me," he once admitted. "When the urge comes, I am helpless."
No wonder it is frequently reported that Douglas suffers from "sexual addiction", having attended a celebrity clinic in Arizona which specialises in treating the condition. Douglas has now let it be known that he will set loose his lawyers on anyone who calls him a sex addict. His time in rehab at Sierra Tucson (which also did a neat job reviving Ringo Starr) was for drugs and booze. So, for the record, Michael Douglas is not sex addict. No, indeed. He just does it a lot.
He often complains that people have confused his life and art, that they muddle the performer with the part. In Wall Street he was a cold predator, in Basic Instinct the sexual plaything of Sharon Stone, an adulterer in Fatal Attraction, locked in a bitter and protracted divorce for War of the Roses. You can see how tongues will wag. Even his own father, Kirk Douglas, observed after seeing Fatal Attraction: "You see, at last you played yourself, and see how well you did."
If there is a tragedy in Douglas's life, it is not that he has been constantly shaded by a famous father, but that he has let his personal failings overwhelm his professional achievements. He has never been the "son of" in that slightly pathetic manner of other showbiz clans. His 1987 Oscar for Best Actor in Wall Street was well won. Before that he had taken another Academy Award for producing One Flew Over the Cuckoo's Nest. In a long career there are surprisingly few duds. In front of and behind the camera, he is a genuine Hollywood star.
Yet there is something irredeemably gruesome about Douglas. There is the periodic bare buttock flashing in his movies, those pale orbs which suggest not so much Hollywood stud as 1950s British naturist film. Then there is his face, a crumpled version of his father's, but with the look of someone who constantly suspects he is about to be found out. Imagine Eeyore caught with nude photos of Christopher Robin. On and off the screen, there is something inevitable about his downfall.
To be fair, he never set out to be a matinee idol. His first job was as an assistant film editor, working on his father's Lonely Are the Brave. After making Cuckoo's Nest in 1975, he moved to television, starring in the crime series The Streets of San Francisco. His real strength, as it turned out, was for playing bad guys or, if not bad exactly, then bleak, abandoned and doomed.
In Falling Down, Douglas was the quintessential angry white male. For A Perfect Murder, last year's remake of Hitchcock's classic Dial M for Murder, he was a homicidal husband. These are the sort of slightly dodgy parts that make many stars, especially the younger ones, wary of their image. Brad Pitt does not go there. Harrison Ford could never even try.
Andrew Davis, who directed A Perfect Murder, says: "A lot of your leading men will not allow themselves to look this malevolent. They don't want to be booed. But Michael likes this." Douglas admits this is the case. "Actresses have more fear of being disliked," he once said. "I, on the other hand, revel in it."
He also has an uncanny knack of putting his foot in it. Almost every notable remark could come back to haunt him. He has complained that it is "difficult for me to meet women because my crowd is much older. I know that for some of the young women I do meet, a relationship can be envisioned as a benefit to their career". Does Miss Zeta Jones understand quite how she is reaping the benefits of a fling with Douglas? Not every young actress sees things Douglas's way. "It's sort of creepy if in real life I'd be married to Michael Douglas," reflected Gwyneth Paltrow about her screen husband in A Perfect Murder. "There's definitely an uncomfortable age difference."
Then there is another throwaway remark of Douglas: "There is nothing like a family crisis, especially a divorce, to force a person to re-evaluate his life." Could he really be so flippant? The answer is, yes. At the time Douglas was splitting from his wife of 20 years.
The couple had parted twice before, over his infidelity, but in 1997 the split became permanent. It was said at the time that what did it for Diandra Douglas was not the womanising and boozing, but her husband's endless quest for self-discovery. She could take (just about) the adultery; it was the therapy that finally ended the marriage. And after it was all over, how did Douglas feel about being single again? "Pretty good. It's a nice sense of irresponsibility."
In his defence, these have been pretty heavy years. While the divorce papers were being filed, the couple's 18-year-old son Cameron did some rehab of his own for substance abuse, while his half-brother Eric was arrested for drunk driving. Then Kirk suffered a severe stroke. During the making of The Game, in which Douglas plays - guess what - a rich, egocentric and ruthless tycoon, the director David Fincher remembers that the star would disappear into his trailer between shots: "On the phone talking with lawyers for his wife, son and brother and talking with his father."
During Michael's childhood, Kirk, who divorced his mother, the British actress Diana Dill, when he was five, seems to have been a lofty, remote figure. "When I was growing up, I was always just Kirk Douglas's son," he once recalled. "I had to fight for my own identity."
The old warhorse is now 82 (and recently completed his 82nd film). His illness seems to have brought father and son together. There was a particularly touching scene last year with Michael supporting Kirk at a Hollywood lifetime achievement award. Both men say they have never been closer. "We're becoming the father and son we never were," says Michael.
Douglas has other things to keep him going. He is a liberal in that rather self-aware Hollywood way but which must also have been shaped by his father, the child of Russian immigrant Jews, who battled the McCarthy blacklist at time when it was not wise to do so. For next year's presidential election, he has placed a $1,000 bet on both Al Gore and his likely Democratic challenger Bill Bradley.
Last year he was chosen as a "messenger of peace" by the United Nations, one of those slightly sappy gestures the organisation likes to make towards sympathetic celebrities such as Ginger Spice Geri Halliwell, Pavarotti and Magic Johnson.
Douglas seems to be taking the whole thing very seriously, saying the title is more important to him than winning either of his Oscars. He wants to campaign for nuclear disarmament and gun control, which sounds rather like the manifesto of a Miss World candidate.
But just when it is all getting a little too precious, the old Douglas makes a comeback. Those photos with Miss Zeta Jones show he has lost none of his old touch. And Michael, even in advancing middle age, remains a charismatic figure.
Such was his impact on Maureen Dowd that the New York Times's chief Rottweiler briefly ceased her savaging of the Clinton White House, under the influence, it was said, of her lover's liberalising effect. The seduction of Miss Zeta Jones is just the latest twist in the plot. You could say that it is part of his Basic Instinct. Just don't call him a sex addict.Reuse content