We were preparing to drive to my parents for the spring bank holiday weekend when the penny dropped that she really was having an affair. 

Bits of circumstantial evidence had trickled past me at growing velocity over the previous few months until I had developed a live suspicion. But there were alternative interpretations for everything. Until that afternoon when she said she was popping next door go give something to the neighbour. That wasn't in itself unlikely. But short pop-outs had become fairly often where until a few months before they never happened at all. So I popped out a few minutes after her and saw her leaning against a wall in the street, busily texting away.

An hour or so later, just before we decamped into the car, she said she had to text her boss at work as he was supposed to bring her something from the office before we left. She closed the bathroom door on our son - and me - so she could do it in peace. That was when I knew for certain.

In March she had suddenly become a lot happier. She'd been fundamentally down for years, since a miscarriage a very long time ago. And even that had followed a prolonged post-natal depression. Then she was diagnosed with a serious disease that has taken two years to deal with and recover from. I was so please by this new sunniness and told her I hoped it meant a new leaf in our relationship. However, the first female I mentioned this to, in early April, immediately suggested she was having an affair.  But at that stage I had no evidence. 

She began buying new clothes and going out with her single mum friend a lot more. But she never bought enough clothes and after a cosmetic breast op last September, needed new stuff that fitted her. Suddenly a password appeared on her phone. Her hotmail and desktop passwords at home changed for the first time, so that neither I nor our son now know them. A webcam appeared for her laptop, so she could skype her friend in Australia.

Then I detected perfume. I love perfume and used to buy it for her, to encourage her to wear it. But she can’t smell, the result of an accident when younger, so it meant nothing to her. Once we had a child, she always neglected to put any on.  She can’t have worn it for years. But still, it was great to see her building new confidence and taking a new pride in herself after years of making no effort as a soap-opera devouring couch potato and gambling online.

In the Easter holiday she said she couldn’t take a week off to go to France for a few days as we had planned because her boss had pipped her to the post with the holiday schedule. So she suggested I take my son away somewhere instead, to help with a project at school. We were away over a Monday and Tuesday evening. She went out for both nights, into town for at least one of them (we're suburbanites), something she normally hates because of the difficulty of getting back. That was when I began to wonder.

The weekend before this, a neighbour had come over to collect his son from playing with ours. As he and I entered the sitting room, she lowered the screen on her laptop so it was 3/4 closed. It was the second time I'd seen her do that. Then when we were chatting, she kept doing some sort of chat thing on the computer, tapping something on the keyboard with one hand and looking down furtively. I asked her what she was up to – she laughed, looked guilty and went red. She claimed she was planning a surprise for my birthday next month and I had to give her some space to get on with it.

For the Whitsun half term, we had also planned to go away but the same thing happened with the holiday rota. She couldn't go. Our son was going away on a school trip two weeks later and we had talked loosely of some time to ourselves that week instead. Maybe 2-3 days away midweek as I work for myself and she has a flexible, part-time mummy-hours job. But instead she unilaterally booked to go away for four nights by herself – 2 to stay with a friend in the Home Counties and and 2 to go to an event with a a newly discovered old friend in the Midlands. This positively rankled. But I know the first friend and have at least met the second friend, so I knew they weren’t purely fictional. Of course, I don’t have contact details for either.

On the drive to my parents my mind churned through likely candidates. Her single friend had recently joined an internet dating site in I think the beginning of March. I’m pretty certain of that because her subscription came up the weekend we went to my parents, so that would be 3 months. Perhaps my wife had joined it at the same time. If so she copped off pretty quickly because it was that month that she brightened up. Alternatively she could have met someone round and about when she was out with her friend. Or there might have been someone she met through work. She works in a small office but travels around the area a lot and deals with a lot of people. 

, the day after we came back from my parents. So if that was a ruse, it couldn't be her boss as he'd be away. So perhaps it wasn't him after all.

Having said that, he came over to deliver the office key just before we left and it was him that my wife said she was texting, so privately, before we left. So in theory that could be a cover story. I thought I might breeze by that office in the week to see if he was there.

The worry affected my sleep. I never have trouble sleeping unless I am under exceptional stress. I woke at 6 the Saturday morning after we travelled to my parents'. The following night we drank and I slept well. But on the night we came home, the Bank Holiday Monday I woke at 3.30am. Tossing and turning I moved off to the spare bedroom. But when I felt I really was going to drop off, I returned to the marital bed. I snoozed but had obviously disturbed her – she sleeps lightly, a curse on our relationship – and she got up just after 5 and went downstairs. At 5.30 I went down and got the blame for having woken her. When I went down to iron a shirt an hour later, she abandoned her computer after 10 mins and took her handbag upstairs to the bedroom with her.

On the Saturday of the Bank Holiday weekend, I had taken her out for a drink by ourselves. She opened up about the well worn problems in our now teenaged relationship. I said (again) that it is her coldness that is the problem in our sexual relationship. We had some laughs, she put her head on my shoulder and I put my arm around her. We talked about ways out of it. In the car between pubs she asked who I was shagging. I explained I had clean hands and loosely tossed in, as I busily reversed the car, that I knew she was shagging someone. “Who am I shagging?” she asked. “Dunno” I said. The subject changed. 

In the car on the way home she said “So what’s the plan?” We booked a date for the following Tuesday, 31st May,  after our son was asleep, and agreed to try to get him a playdate on Saturday so we could spend the night together. 

But driving back in the car on Bank Holiday Monday night, I mentioned those dates. She seemed startled but acquiesced. When we got home she mentioned how tired she would be the following day (the Tuesday) but acquiesced again about our date on Saturday. When I mentioned that we had decided on a number of things to do on coming Saturdays, she pointed out ominously and repeatedly how very busy things will be before the summer holiday.

Having woken so early she was in a foul mood on Tuesday morning. Before leaving for work she snapped at me about getting a new job and earning more money. I asked if that would solve the problem. She said it would at least stop me hanging around the house and being very concerned about what she is doing. I said “And we know why I am doing that, don’t we?” There was no reply.

That morning I tried to concentrate on working but my nervous system felt like it was in an acid bath. Not just an impoverished old age beckoning but the loss of my beautiful boy. I checked the public profiles on her friend Diane's singles website but didn't find her. I called my favourite ex-girlfriend, who once left her husband for another man for more than a year. We agree that the best thing is to play it long. “When I left Jason, it was because his wife discovered and forced me into a choice. The affair was still on the upswing and I chose not to let go. It was a mistake, these things always blow over in the long run. If I knew then what I know now about how it would affect my younger child, I wouldn't have done it. But I hadn’t been planning to leave, I was just after a bit on the side. I didn’t realise that then but I do now”.

I said that although I'd prefer to talk about it with my wife and try to agree some rules about how, while the affair lasts, I will give her space in exchange for a definite list of commitments; my instinct is that it is best to say nothing and let the thing eventually blow over on a least said soonest mended basis, however painful it will be to pretend not to notice the gaping holes in her stories. We called that Plan A. Unfortunately, as I had mentioned her cheating in two conversations in the previous 3 days, it may no longer have been possible. We designate the negotiate strategy Plan B.

But my wife came home at lunchtime as if nothing had happened and nothing had been said that morning. She want back to work in the afternoon and came home again equally placid. We were invited out for an impromptu meal with our neighbours and their boys that night. It was a wonderful evening with a fair smattering of alcohol all round. Back home, I didn’t make a pass as we were both knackered and had eaten curry. But it looked as if Plan A was intact.