With One Born Every Minute (Channel 4) returning for its sixth series, I'm going to hazard a bold assertion: as a form of entertainment, this whole childbirth business has legs. You'd have thought they might have run out of permutations and complications by now – birthing pool, C-section, breech, what's left? But it's like MasterChef: repeatedly absorbing, even inspiring, while still making you feel pleased to be sitting on a sofa in front of a TV. I've certainly never felt like cooking anything after watching MasterChef.

This time we're at Southmead hospital in Bristol, so we've got jolly West Country accents to lighten the mood. Su and Dan Belcher are arriving in the dark, giddy and expectant, clearly some way off labour proper, which instantly brought back memories from my distant past. "Is it too late to do a runner," says Su, "and go to McDonald's instead?" Many years ago my wife had a similar idea, but she made me stop at a drive-thru on the way – a decision she would come to regret within hours.

Su and Dan, it transpires, are so calm because their impending daughter Chloe is breech, and a C-section is scheduled. For them childbirth is adhering to a timetable.

Rob and Katy, meanwhile, have other plans. Katy had an epidural with her last baby, and as a result felt quite detached from the process. This time she is attempting a natural birth, but she's not really selling it to me, to be honest. It looks like a process I would prefer to be detached (or even wholly absent) from. Mind you, I'm not flipping over – unlike the imminent Chloe. "Chloe has flipped," Dan Belcher tells relatives on the phone. A scan has shown that Chloe is now pointing head down, making a caesarean unnecessary. Su's composure instantly deserts her. Her last experience of birth was so traumatic she had trouble bonding with her baby, and she now has a long, dark night ahead of her.

Late arrivals Mel and Chris are having twins. Chris is interviewed wearing a T-shirt announcing him as a Gallifreyan Time Lord, which I feel safe in saying is something we haven't seen before. Much is made of the fact that this will be the fourth consecutive generation of twins in Mel's family – Mel is herself an identical twin – although I think the potential regeneration of twin Time Lords is the bigger deal.

In the end Chloe is born safely and in circumstances that allow her dad to sleep through a large part of the proceedings, in the same room. The Gallifreyan twins are delivered by C-section, and Katy manages to give birth standing up, which is one of the most impressive things I've ever seen. Six series on, One Born Every Minute is just as gripping, charming, moving and NHS-affirming as ever, and I still cry reliably, shoulders shaking, three times per episode. That hardly ever happens with MasterChef any more.

Eight years ago filmmaker Chris Terrill – then in his 50s – trained alongside Royal Marines, earning their friendship and trust before accompanying them to Afghanistan for the documentary series Commando: On the Front Line. In Commando: Return to the Front Line (ITV), Terrill went back to Afghanistan with Bertie Kerr, a former officer who back in 2006 found himself commanding soldiers in Helmand just weeks after completing his training.

The original documentary (footage from it forms a key part of this one) spanned a sobering period in the conflict: when Terrill started filming, only one British soldier had been killed in combat. By the time he and Kerr were ready to ship out, that number had climbed to 21. And the next soldier to die would be one of Kerr's men.

Kerr now works in the City, and had mixed feelings about returning to Afghanistan. "I had thought I'd seen the last of the place," he said. Camp Bastion, where he'd spent much of his time, is now in the process of being dismantled (one dumping spot is signposted "Warlike Scrap"). He and Terrill visited the Afghan army training camp next door, but it doesn't offer much scope for optimism. Half an hour after they left, a recruit opened fire on an instructor.

Inevitably, the death of Kerr's friend Tom Curry, shot by the Taliban while under his command, loomed large in his recollections. His soldiers ended up killing all the Taliban they encountered that day – men as young as themselves. "I took the hat from the one I shot," said Kerr. "Those little caps they all wear. I don't know why."

The benefit of hindsight made this an incredibly powerful programme, a grim reminder of war's cost from people who, at least in part, paid the price.