John Lennon had previously filed for divorce, alleging that Cynthia had herself been adulterous - a charge she denied.
I had to survive this for Julian. I couldn't afford to crumble: I had to be strong, do what was best for him. I could fight the divorce, but that would get horribly messy and in the circumstances as clean a break as possible seemed best. By dawn I had made my decision. I would countersue for divorce, citing his adultery with Yoko.
Lennon did not contest the order, and the divorce was granted in November 1968.