I doubt he was sober at any time surrounding the death of Diana. A functioning alcoholic who has lied so many times it's hard to know when the truth is there.
He is jealous of KC because in his mind, if Lord Mountbatten hadn't put a stop to it, his Daddy would have swept the future Queen off her feet and Charles Spencer would be king. Of course, that whole scenario is just another lie he tells, like his lie about how he would never profit off Diana's death. And though he might have "won" the battle about offering a place for Diana after her divorce; the truth is, he offered a decent place for her to RENT, then reneged, then offered one of the downtroddened farmhouses for her. For a hefty rental fee, of course. Until she died, he had little to do with Diana, nor she with him, but after her death, he acted like he was with her daily; then decided she should be buried at Althrop so he could control her, even then. Maybe hoard is better than control?
I do not believe a word he says. With his ex-wives, DV accusation, mistresses, children who are NC, his lies, his life in the bottom of a bottle, I'd be more likely to believe Bryan Kohberger.
There are no 'perfect liars' in the world; there are only 'perfect believers' who believe in even the most obvious lies!