I decided I was going to ask for a divorce within two weeks of the defining moment (we'd had some discussion about it afterward, but I think he thought we were just going to limp along as we always had). Then XH went away on a business trip, and being alone gave me time to think.
I had to wait another 2 weeks to tell XH because I had friends coming to stay with us and I didn't want them walking into all that. It was so hard. We went over to Paris to see XH at the end of his business trip and I had to try to act normal, all the while knowing what I was going to do. Very hard being alternately irritated and sad/nostalgic. I kept being tearful and he had no idea why. Finally told him when we were back in the UK and he wasn't all that surprised.
We took separate bedrooms in the same house from then on, but I tried to be out of the house a lot for the next month, staying at work or with friends. Then I went to the U.S. for 3 weeks and when I came back I was essentially living with a guy from work who I started seeing (now DH2).
XH was supposed to move out of our house and I was to get a lodger, but suddenly he refused to, so I continued to stay with boyfriend for a bit then got a room in a shared house for a while. XH got a lodger.
We had a huge ongoing battle about selling the house that finally had to be resolved in court, then the divorce was final a few months after.
So from defining moment to decree absolute, it was almost exactly 11 months.
I can't believe it has only been 2 years since that. It feels like a lifetime ago. Only wish I had done it sooner, but I feel like at least I spent 4.5 years REALLY trying and we had all the therapy we could afford.