“If I live to be 100, there will still be so many things unsaid,” Kirk Douglas wrote to his wife, Anne, in 1958, four years after their marriage in Las Vegas.

After marking his 100th birthday on December 9, 2016, the movie star wrote: “As I have now reached that milestone, I can attest that it is still true.”

Both declarations are included in the couple’s newly published book, written with Marcia Newberger, Kirk and Anne: Letters of Love, Laughter and a Lifetime in Hollywood.

The book, Mr Douglas’s twelfth and his wife’s first, chronicles the ardent, if sometimes stormy, relationship between two strong personalities, he the son of a hard-drinking Jewish immigrant ragman; she the daughter of a prosperous German family.

During his 60-year film career and some 90 movies, Mr Douglas was frequently away for long periods on location shoots, and husband and wife wrote to each other constantly.

Fortunately, the couple started writing on actual paper stationary and continued the habit even after the start of the email era. Secondly, Mrs Douglas kept every letter, preserving them in the couple’s wine cellar in Beverly Hills.

Along the way, the reader learns not only about the couple’s love life — including Mr Douglas’s infidelities with various movie queens — but also about the affairs of fellow Hollywood stars, sparing few graphic details.

But that’s only part of the book. The couple befriended US presidents and their wives, from John and Jackie Kennedy through to Ronald and Nancy Reagan and Barack and Michelle Obama.

The Douglases also played and worked with LA’s rich and famous and cast a frequently jaundiced eye on the predominantly Jewish magnates who dominated the studios, before these transformed into bland corporations.

The couple married in 1954, and when she was asked if she would take Mr Douglas as her lawful husband, she replied, in yet imperfect English, “I take Thee, Kirk, as my awful husband.” After the laughter died down, Anne explained that she thought the word meant “full of awe”.

Despite this rocky start, in 2003 and after 49 years of marriage, Mrs Douglas decided, on her own, to convert to Judaism. In a recent interview with this correspondent, Mrs Douglas described her mikvah experience: “After removing all nail polish, I put my head under the water. I came out looking like a wet dog — but I was Jewish.”

She announced her new status at a full-scale religious celebration, marking the couple’s 50th wedding anniversary. “Kirk has been married to two shiksas,” she said. “It is time he got a nice Jewish girl.”

Mr Douglas has developed his own definition of Judaism. “I grew up praying in the morning and laying tefillin, but I gave up much of the formal aspect of religion,” he said. “I believe in God and I’m happy to be a Jew. But I think too much religion has not helped civilisation. Caring for other people is my religion.”