The Wall Street actor began dating the Welsh actress, 25 years his junior, in the late ‘90s, with the pair marrying in 2000. Despite a short separation, 72-year-old Michael believes the longevity of their relationship is down to the sense of humour they approach their age gap with.

"We joke all the time about when I reach my 80s and she’s wheeling me around and I’m saying 'Whoa, where are we going?' And she will say 'Cartier darling, Cartier. It’s your favourite store,'" he recalled to U.K. host Jonathan Ross. "Remember, to keep a sense of humour about these things."

When asked if the age difference was difficult, Michael said he wouldn't use that word to describe it, adding 46-year-old Catherine will look him in the eye when he forgets a name or a date and he'll reply, "Yes dear, I know'".

The Basic Instinct star spoke during a special interview event, An Evening with Michael Douglas, in London on Sunday night (30Nov16) during which he discussed his battle with cancer.

He was diagnosed with stage four tongue cancer in 2010, although it was first announced as throat cancer. He underwent a course of chemotherapy and radiotherapy and has since been given the all-clear but admits his taste buds have changed due to the treatment and he can't enjoy certain foods and drinks as he did before.

"Red wine does not taste as good (as it used to). It’s a small problem," he shared. "Spicy food does not bother me as much as it used to. I have certain things I stay away from. I can do beer."

He also hinted actor Val Kilmer has suffered with the same disease by saying, "Val was a wonderful guy who is dealing with exactly what I had, and things don’t look too good for him... My prayers are with him. That’s why you haven’t heard too much from Val lately."

Val, who has previously denied having cancer, addressed the rumours in a Facebook post on Monday, quoting Mark Twain, who the actor is playing in a new project.

"'The recent news of my death has been greatly exaggerated...' MARK TWAIN. And his values and spirit live on even now! And I'm sure still standing! Yippee!" he quipped.