My laptop wouldn't work and I needed to do some banking so I texted him to ask if I was ok to use his. He replied and said yes. So I did.
I went to clear my history, as I always did on my own laptop, and there was a single webpage in his history for a NSA sex website - I assume he normally used incognito browsing or also deleted his browsing history, which was why he was ok with me borrowing it.
I clicked on the link - he had a profile on there. And I could see which profile's he'd looked at.
I don't know if he had ever met up with anyone but the intention was enough for me.
I messaged him with a copy of the link and "care to explain?" He read the message but didn't reply.
So I rang him on his desk phone at work for the first time ever. His colleague answered and told me he had gone to the loo, so I said I'd call back. I tried again 5 mins later and his colleague told me he'd gone into a meeting. So I told the collegeague that my husband had precisely 5 minutes to call me back or I'd call again and tell his colleague exactly why I was phoning him at work.
He called me back immediately.
I kicked him out the same day.
There were no other signs. I'd never have known had my laptop not failed. Oddly, it worked fine the next time I tried to use it. The universe was looking after me that day 