I wasn't quite the cliché father for the first six months after K      was born, going back to work a couple of weeks after the birth thinking S      was having an easy time hanging out at home whilst I did the harder job of bread-winning. Going to work always felt like the easier option.

But nor, I discovered when I took over six months later, was I quite as far from that cliché as I would have liked. I could understand how physically exhausting night after night of disrupted sleep and very early mornings were. But I didn't understand how mentally and emotionally exhausting it is taking care of a young baby on your own. Until I was doing it myself.

When it came to my six months taking care of K      full-time, by the end of the day I'd be counting down the minutes until S      got home from work. More often than not, within moments of S      getting home and scooping up K     , I'd crash on the sofa and fall fast asleep for half an hour. Not because I hadn't got enough sleep during the night.^{33 3}S     's attitude was that she had to be up in the night with K      anyway, at least during the earlier months, and there was no point both of us being wrecked. And not because I hadn't had a great day with K     . Just because taking care of a young baby demands your full attention almost 100% of the time they're awake. Or at least, K      did – usually quite vocally!^{44 4}Not necessarily by crying. From early on, she was very good at making it clear she wanted to show us something, or do something, or be picked up, or be shown something, or play with something. Perhaps we brought this on ourselves, by giving her our full attention when with her. But hey? What else would you want to be doing whilst on full-time parental leave? The evidence backs this up as a positive thing, albeit a more exhausting one than leaving them in a high chair or bouncer much of the day.

Everyone who's taken care of a young baby on their own knows there's no taking a five minute break from being a parent. Even naps are limited respite: time to sterilise bottles, prepare food, have a shower, go to the loo(!), fight a losing battle against the entropy babies are experts at generating…just in time for K      to wake up. It's relentless, even when it's rewarding.

Perhaps some people are sufficiently empathetic to understand this without having done it themselves. I'm not one of them. Talking to other mums (invariably mums), this is the one thing people consistenly told me their partners didn't understand.^{55 5}A recent collection of interviews with fathers who took some paternity leave echoes this.

One evening, a couple of months into her maternity leave, S      was lameting that it was going by too quickly. I tried to reassure her, pointing out she still had over two thirds of it left. Fast-forward to one evening a couple of months into my paternity leave. Now it was me lamenting that it was going by too quickly.

Taking care of K      full-time profoundly altered my relationship with her, and her relationship with me. During the first six months, I enjoyed hanging out with K     . But I didn't experience that close emotional bond you're "supposed" to feel as a parent – the feeling that I'd throw myself under a proverbial bus for her. I was still determined to take my share of the parental leave. But it was more because I felt it was right, than because I was desperate to take care of a six-month-old on my own for much of the day.

It's a far more common experience for new fathers to feel they're not bonding with their new baby than most people let on.^{66 6}Or, worse still, to suffer from post-natal depression, which is roughly as common amongst fathers as it is amongst mothers. Though it's less well studied, so the data are sketchy. Watching your partner and baby's rapidly-deepending relationship, it's easy to start worrying there's something wrong with you. Or to start believing that mothers are biologically programmed to feel this in a way fathers aren't. I was lucky in that my brother had talked to me about his similar experiences of early parenthood. It was immensely reassuring to know I wasn't alone in experiencing this.

Just a couple of weeks into my paternity leave, and this had changed completely. Turns out the quickest way of forging a close bond with K      was – surprise, surprise – to spend a large amount of time with her one-on-one and take on primary responsibility for caring for her.

I love my job.^{77 7}The research and teaching parts, at least! On paper, those are my main roles. Sometimes, I have the impression someone misread that as: "your main role is to produce paperwork"… And I'm even more enthusiastic and excited about science and research coming back to it fresh from a six month break. But if someone had offered me a four-year career break, with a guarantee of my academic post back once K      was at school, I'd have taken it. That's something I never would have expected – and never would have felt – had I not had those six months full-time with K     .

Sometimes through circumstance, but just as often through choice, the overwhelming majority of fathers don't currently get the opportunity to experience this. I wonder how many would rethink how they balance work and children if they did?

…I wish I'd done a couple of weeks of childcare on my own sometime during the first few months. That would have been enough to appreciate what it's really like – both the exhaustion and the fulfilment. I propose making this a legal obligation for all new fathers.

The first time around, I wanted to split the parental leave equally because it seemed fair. Next time around, I want to split the parental leave equally because I want my six months!