Ok. First of all thanks to everyone. This support has been amazing and it's useful to get different perspectives on it. It's also good that on here people will say "Do you really believe he hasn't had sex with her?" whereas in real life they might bite their tongue.
I need to thank MN for alerting me to the clues or this might never have come out - In his case -
Sudden increase in personal grooming
Taking his phone to the toilet
Suddenly critical of me when he's normally kind
Moody in social gatherings when he's normally life and soul.
I started to check his phone/ FB etc and the same name kept on croppping up. I confronted him when I had kept hold of his phone late one night and she started sending messages. Nothing too damning, but my colleagues never texted me to say "night night" at 11pm.
He admitted an attraction and sending one mundane gift. I dug around and found evidence of an additional (expensive) gift. He then admitted to others and finally admitted that when they were to meet at the conference, something might well have happened.
I've gone through everything with a fine tooth comb (I used to be a detective before DC, so I'm pretty sure I've covered most things. I've checked his phone, lap-top, work receipts (I even phoned the hotels he's stayed at to check whether the rooms were double or twin
). He has given me access to his on-line accounts and I have checked his wallet for additional credit cards (god how did we get to this
).
I've called his bluff by demanding that he send her a suggestive text to see what response he gets and he agreed. I obviously stoped it before he pressed send.
He is utterly devastated and I am sure that is genuine. He has definitely been having some sort of crisis before this started with lots of pressure at work etc. We were not as close and he says he was flattered by the attention from a younger woman. I do not think there was any sort of deep connection between them - she works in a different country, so their meetings have been infrequent and I am as sure as I can be that nothing has happened physically between them. It is bad enough though that he has admitted that it probably would have if I hadn't sussed him.
I have decided not to tell my family at this point though I have told him I may. He has told his sister who is a battle-axe and has given him an earfull. I have confided in one good friend who I know I can trust and who will give me some straight talking.
He is sleeping on the sofa (the DC will be told because he snores) and we are going to have some counselling.
I'm sure some people will think I am a fool for taking him back in to the house. But I guess I want to try to make it work for the sake of the DC if nothing else. If we can't restore the love and respect then so be it, but at least we have tried.
Thanks again to everyone and wish me luck.