Roy and Keeley announce they're getting married. Roy is obviously planning to ask Jamie to be best man, but all the Diamond Dogs and Rebecca and many of Roy and Jamie's former teammates are like "nooo you shouldn't do that. Don't Do That." Roy and Keeley, naturally, are very upset. "What do you mean we should exclude Jamie?! We can't exclude Jamie! It's Jamie!" "I'm not saying exclude him just maybe...don't ask him to be best man. I mean, don't you think that would be kind of hard for him? Being so involved with your wedding when he's still....." Now Roy and Keeley are confused. Jamie's still..? Still what? He's fine! They talk to him all the time. Yeah, he's kind of dodged their last few invitations to come visit, and they've heard from him a little less, lately. They're usually the ones to reach out, come to think of it, and that's a little weird. It never used to be that way. Maybe someone finally comes right out and tells them, "Jamie's still in love with you." but they brush that off immediately. It can't be. Jamie moved on from Keeley ages ago...didn't he? He's never been in love with Roy. No, it can't be.
Flash forward to the lead up to the wedding. Roy and Keeley, against all advice, have asked Jamie to be best man. Jamie, against all advice, has accepted. Even though he's been distancing himself, purposely. Even though he's been working so hard to move on, and he thinks it's actually been working! He's doing better. He's happy for them. Which means this will totally work, right? He can separate himself, emotionally.
When he flys back to London, he ends up staying with Roy and Keeley. Naturally. Roy and Keeley's colleagues/friends all have their heads in their heads. "He's staying...in your house? Right before your wedding?" "Well yeah, where the fuck else would he stay?" Anyway. Long story short there are many revelations that week and they fuck right before the wedding and Roy and Keeley have a crisis about whether to still go through with it.