Neil Sinclair has spent six years in the commandos. He has survived winters in Arctic Norway, cleared minefields in Iraq and tracked drug traffickers in the jungles of Belize. He has guarded the British mission to the United Nations in New York. But he has never felt so panic-stricken as when he was facing a howling two-month-old at 3am.
''I guess that's when the idea was born,'' Sinclair says of his sensible and accessible new guide to parenthood, Commando Dad. ''When we brought our first child home from the hospital everything we had read and everything we'd been told up until then was about the birth - and now here we were, back at home, with a new baby, and I hadn't the faintest clue what to do.''
Sinclair, 41, now a father of three, found himself wishing for something he'd been given when he joined the army: a basic training manual.
''Any soldier will tell you how precious that little book is,'' he says. ''It's a survival guide, basically. It tells you how to do everything you have to do - simply, clearly and concisely. So that was my plan: a book that will tell dads exactly how to bathe a baby, change a nappy, make a bottle, give it. A book that will give them confidence.''
Most parenting blogs, books and websites aimed at fathers, Sinclair says, ''are gimmicks … They lose me very quickly. I switch off. At two in the morning you don't want to have to plough through a chapter. There's this little thing in front of you, completely dependent, and you're lost. Worse, you can't think straight, with the noise. You need to be told what to do.''
Commando Dad sets out to offer ''a few essential skills, to reduce the stress, and allow you to function''. The tone is cod-military and tongue-in-cheek, referring to a dad's ''mission'' and to newborns as BTs (baby troopers).
Chapter headings include: Preparing Base Camp (baby's bedroom); An Army Marches on Its Stomach (feeding); Welcome to the Thunderbox (toilet training); On Manoeuvres (transporting kids) and Dealing with Hostilities.
''It's 'Right, gentlemen, today's lesson is … burping baby,' '' Sinclair says. '' 'For this task, you will need equipment A and B. The core skills you require are X and Y. Here are the key dos and donts. And then: fall out, commando dads.' ''
This may not be to everyone's taste but Sinclair is sanguine: ''For me, a new dad is a new dad, whether he's from a housing project or upscale Kensington [London]. That's the real leveller. I've just tried to make my book as useful and relevant as possible to everyone.''
The advice, approved by health care professionals, is quick to read, easy to understand and simple to digest, delivered in short, unambiguous bullet points and, no-nonsense rules - and, pretty unarguably, spot on.
''Because this is a very serious task, and a mission that lasts a lifetime,'' Sinclair says, slipping into commando-speak, ''There's absolutely no more important job to do well and get right than being a good dad. It's about doing the best you can, every day and in every situation. And that's not easy.''
No one could say he doesn't know what he's talking about. Besides having three children - Samuel, Jude and Liberty - Sinclair, since leaving the army, has worked as a PE supply teacher, a stay-at-home father (his wife, Tara, is a PR executive who helped ''tremendously'' in the writing of the book) and as a qualified childminder.
In fact, it's been far from what you might call a standard-issue career: a brace of school academic qualifications; 59 Independent Commando Squadron; teacher training; and three years in security in New York after Tara landed a job with an international PR company.
The family later came back to Britain and Sinclair became primary carer for the couple's two children, followed by a third.
Being a stay-at-home father, he says, laid the foundations for the project: ''We made the decision, when we came back to Britain, that one of us would stay at home with the kids. Whoever got a job first would work. So I became the main carer. I feel really privileged. And it didn't half teach me a lot.''
Then, Sinclair says, he started to feel he wanted to contribute more financially while staying at home; he decided the best way was to train as a childminder. But that in itself presented a number of hurdles. ''People just didn't get it. I had to explain time and again: Look, I have two kids at school, and a daughter still at home. I'm at home all day with her. I want to bring in money, to offer a positive male role model and to allow someone else to pursue their career. Is there really anything so terribly wrong with that?''
Childminding, he says, taught him even more: ''It's hard work. But it taught me the importance of being organised. If you can get organised, you can have fun.''
Organisation, unsurprisingly, is a core element of Commando Dad. ''Preparation and planning prevent poor parental performance,'' Sinclair says, subverting a military axiom. ''Think ahead. Be prepared for all eventualities, but have the confidence to adapt. Have your kitbag squared away and ready for deployment. Recognise that good routines should be standard operating procedure.''
Other top tips? ''The golden rules,'' he says, ''start from the fact that a commando dad is a hands-on dad. He gets involved, he takes his responsibilities seriously. He's engaged, he spends time with his kids, caring for them - and he gets the information he needs to do it.''
It may be couched in unfamiliar language, but this is all sound common sense. And even the most pacifist-minded of dads can see that the military metaphor works surprisingly (and entertainingly) well.
There's a website to accompany the book (commandodad.com), with a forum and a blog, and Sinclair is contributing to sites such as Mumsnet. ''There are,'' he says, ''a lot of dads out there. We have to share our tips and experiences. No one ever knows everything. Even the SAS has back-up.''
Just as in the army, he says, morale is key: ''I have a whole chapter on morale. It's crucial. Don't be hard on yourself. We all have bad days. Just because you make a mistake, doesn't mean you're a bad parent. And above all, don't be afraid to ask for help. You're never on your own, and you're no less of a dad - or a man - if you ask for help.''