I’m sure that only the most steely, focused and disciplined people can actually stick to their New Year’s resolutions. So, as I have none of these very valuable attributes, being weak-willed and capricious, I was particularly pleased to have reached the middle of February with my one 2014 promise still intact – that I would stop biting my nails.

OK, I still had the odd little nibble now and again (it’s a nervous habit, possibly even an addiction, so try not to judge me too harshly; at least I don’t smoke crack or drink paraffin at bus stops) but generally I was thrilled that my finger ends no longer looked like the bald heads of those old-fashioned clothes pegs my mum used to use.

I could proudly wear that rather nice statement ring I bought at Christmas for £10 (I love a bargain); I started to think that I might even try a little dab of nail polish. But it was a short-lived dream. All it took was the first episode of Jed Mercurio’s Line of Duty and once again I was dining on my fingertips.

Dear me, Line of Duty is so exciting that it makes me bite my nails even when I’m not watching. I bite my nails just thinking about Line of Duty. I’m biting my nails right now, which makes typing terribly difficult.

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The first series in 2012, despite some major plot holes, was terrific and became BBC2’s biggest new drama in ten years. The second, though, is sensational. Don’t fret that you’ll need to watch series one first if you didn’t see it – you don’t, although I would heartily recommend you do so just for sheer pleasure.

Some of the key characters remain – the cops who investigate other cops to root out corruption – but it’s an entirely new story. Its focus is Detective Inspector Lindsay Denton (Keeley Hawes, who is excellent, looking all drab, wan and put-upon). She might, or might not, have orchestrated a murderous ambush in which three colleagues were killed and a man under witness protection grievously wounded. Certainly the evidence points to her as the plotter… or does it?

What I love about Line of Duty is that it’s a big, grown-up game of snakes and ladders. Just when you think you’ve got it all worked out and you’re on a roll, scurrying up that big ladder, oh no! – you hit a snake and you slither back down.

It’s a tremendously audacious piece of writing from Mercurio (who wrote the jaw-dropping Bodies and Cardiac Arrest). I won’t go into detail but there’s a staggering scene in the first episode that only a really switched- on and confident writer would even think of attempting, let alone writing. I was breathless by the end.

And episode two left me pleading, to no one in particular, “Please, I want to watch the rest of the series right now because I NEED TO KNOW WHAT IS HAPPENING”.

I love that Mercurio is toying with us, hurling us little bones every now and again, making us think we can trust someone, then they go and do something that leaves us pondering whether we really know them at all. Then we go back to trusting them again.

It’s all so exhausting, but in such an exhilarating way. I end up feeling like Inspector Clouseau: “I suspect everyone! And I suspect no one!” And I’m biting my nails yet again.

Caution: Men walking

You know how it is. You decide that you must head into the country for a bit of fresh air, so you lace up your hiking boots and strike out into the gorse, not another soul around for miles.

Or so you think. But what’s this? Hordes of male TV presenters block your path, all making the same outdoorsy documentaries. (I had a go at Robson Green not so long ago for this very thing.)

Now, I love the Northumberland coast and its twin delights of Holy Island and the Farne Islands. But Neil Oliver visited both in his recent BBC2 series Sacred Wonders of Britain and this week Tony Robinson in C4’s Walking through History also gazes at them in awe. Both were following in the footsteps of doughty hermit St Cuthbert. Apart from my increasing aversion to Men Doing Things-type documentaries, maybe these paths don’t need to be so well-trodden.

Line of Duty tonight at 9:00pm, BBC2

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