What sort of man was Neil Armstrong? It’s a question that few of us have been tempted to ask, mere mention of his name being enough to trigger a corresponding pop fact appearing in our brains that he’s the first man on the moon, and that satisfies any curiosity about him.

Buzz Aldrin though. Now, there’s a tragic figure. He spent the rest of his life in Neil Armstrong’s shadow, and never emerged from it strongly enough to establish his own identity in anyone’s mind – most especially his own.

I’m pondering astronauts because I’ve been watching a one-off episode of Wire in the Blood, the show about kooky criminal psychologist Tony Hill - a fine performance by Robson Green. Now, there’s a man who knows how to cover his traces – the strength of his acting is such that I barely think of his singing career as part of Robson & Jerome, a double act coaxed into something other than life by necromancer Simon Cowell.

Like your astronaut, your crime show needs something about it to remain in the public consciousness. Morse had his classical music, that Jag, and gruff interactions with Lewis. Resnick had jazz and deli sandwiches. Prime Suspect’s Jane Tennyson was the woman DI with the drink problem.

This, you’ll gather, is all in the realm of branding: establishing the nature of your show’s protagonist with broad brush strokes so they won’t be mistaken for anyone else. No chance of that, when you’ve got big old Robbie Coltrane playing Fitz in Cracker with his gambling, womanising, and the rest. But who exactly is Wire in the Blood’s Tony Hill? He’s got some of Fitz’s idiosyncrasies, a tendency to something like Asperger’s perhaps. And - contrarily - there’s a touch of Columbo about him too, playing low status to advantage; in last night’s episode breaking the inside door handle of his hire car and using the awkward moment that followed as an opportunity to ask some pertinent questions.

Beyond that, I’m pushed to define who Tony Hill is. The nearest we get to a definition is the running theme, explored visually in many opportunities, that Hill is an empath: we see him in tricksily-shot situations echoing ones occupied by others, identifying with killers, victims, and whoever else. It was reinforced in last night’s show by a bit of dialogue: ‘That’s my job – the imagining of pain’, and it’s there in the show’s promotional strapline too: ‘Get inside the mind of someone who’s out of theirs’. But that’s problematic frankly: saying your protagonist’s Unique Selling Proposition is that they blur the boundaries between themselves and others is another way of saying they’re just not distinctive characters (in advertising terms, it’s like Coke admitting that their fizzy brown liquid tastes rather like Pepsi). And in many ways Tony Hill isn’t strongly distinctive. He’s vulnerable, flawed, and not too long ago in the last run of the series was recovering from a brain tumour.

OK, so Tony Hill is not a conventionally strong character, but maybe one suited to today’s viewers, willing to embrace a hero’s flaws and all that (see House, Monk). At any rate, what we’re left with – we hope – is strong writing and performances. And Robson Green is a reliably strong actor in this role, willing to stretch himself in ways that many leading men would be unwilling or unable to do. As for the stories, they’re variable: I’ve seen good episodes and I’ve seen weak ones. Some are based on books by Val McDermid – I’ve not read any – others are originated for the show.

Which leads me to think that the most distinctive feature of the show is its enigmatic title. What does Wire in the Blood mean, exactly? In one interview, Robson Green mused it was an allusion to a genetic kink, the sort of quirk that might give rise to the cases that Tony Hill is asked to deal with. Which wasn’t necessarily what T. S. Eliot had in mind when he used the phrase in one of his poems. I’m willing to bet it wasn’t one of the ones about cats.