I had a gut feeling and was checking his phone in the night. Nothing but one message from who I suspected, the rest deleted. Checked call log, nothing. But he forgot to delete the frequent contacts list, and there she was in the top spot. Her number was jotted in the back of his work notebook too.
I then saw in the diary a note for random initials birthday with three alarms for it! She was a family friend so knew when hers was.
All very subtle, but enough to back up his enormous overnight personality change and what i now know is the script.
Went on denying it for months but suddenly didn't love me anymore after 20 years.
Her current partner, also my friend, called her and she denied it too, but he then asked her to look out the window. He was calling her from outside her house, and sat on the bonnet of my exh car who was inside with her.
These two twats live together now, and I was put through the divorce from hell. Life is better without these toxic people though, even though I see him for child contact still.