Ironically it was Jerry who sued for divorce, only to find the High Court agreed with Mick's legal team that the marriage was not legal. There was a settlement which was called an annulment settlement and part of the agreement was keeping the details secret.
She's not even 60 yet, so why is she marrying an 84 year old man? I'm not saying they're not in love, but can only think it's as much about being companions as anything else. The speculation is that he will settle money on her as part of a prenuptial agreement, which she'll have no reason to spend a penny of during the marriage. He's so wealthy that even if he only settled a small fraction of his wealth on her, his family would be unlikely to notice.
I know it's shallow, but I don't like to think about them having sex!