He thinks he has some sort of explanation for knocking Nigella about and has sent her a legal letter threatening to reveal them.
www.dailymail.co.uk/news/article-2477233/Saatchi-legal-threat-tell-Nigella-really-broke-up.html
Apparently when they got together she gave him 'certain assurances' which she failed to keep and he reckons that it justifies his behaviour.
There's no excuse is there? And given that he works in PR doesn't he realize this is all making his PR skills look a bit, er, shit.