Last Night's TV: Hunting Britain's Most Wanted/Channel 4The Shadow Line / BBC2

When Julian Assange was charged at Westminster Magistrates Court, he arrived in an unmarked police limousine, almost entirely unnoticed by the hordes of photographers waiting outside. Their attention had been taken, instead, by a different car – the decoy, all screeching sirens and flashing lights. "I said no one would ever fall for that," mused Detective Sergeant Mel Humphreys. "All those experienced hacks out there."

In the event, they did get a few pictures: within minutes, a snap of the back of Assange's head being escorted by Humphreys's ear was broadcast around the world. It took the top spot on the BBC News website, much to the amusement of Humphreys and his colleagues at Scotland Yard's Extradition Unit. Just underneath, sat the other big story of the day: the extended wranglings over Shrien Dewani's extradition, also being handled by Humphreys.

Such prominence is unusual. Fascinating though the toing and froing of Assange and Dewani may have been, the overwhelming majority of the unit's time is taken up by other matters: tracing and arresting the various criminals – dangerous or otherwise – that European countries have requested be returned. Going after the most famous bandits you've never heard of, if you like. Or, as Channel 4 would have it: Hunting Britain's Most Wanted.

In truth, these small fry were far more interesting than their celebrity equivalents. The famous ones are much too visible to risk making an escape; they're not going to hop on the back of the exports lorry to begin lives as fugitives. Not so the 100 Albanian offenders living and hiding in the UK. Or, for that matter, any of the other 500 criminals arrested by the Extradition Unit each year. Catching them is sort of like an extremely unglamorous version of Miami Vice: lots of going undercover in grey sweatshirts and fleeces, lurking in suburban back alleys and eyeing up suspicious kebab shops. Instead of car chases, Humphreys et al spend their time following buses. "Where's that effing bus gone?" they exclaim intermittently. Confrontations, when they arise, tend to take place outside high street bank branches, discount stores, fruit and veg stands. It's a Guy Richie film waiting to happen, only with less mockney.

The suspects, when they're caught, are infinitely underwhelming. Even the incredibly wily, like the Albanian Marash Gjoka, who's wanted for murder and has been living undercover in the UK for decades, or the horribly dangerous, like the Lithuanian who recently raped and tortured two teenagers in a six-hour ordeal, are disappointing. The former, at least, looked a bit like a washed-up war criminal: all jowls, tufty white hair and the slight, smug, acknowledgement that yes he was a Very Bad Man Indeed. Mr Lithuania, on the other hand, looked like a confused schoolboy. Likewise, the French serial rapist they caught shortly afterwards. It was hard to believe that this was the "very violent offender" for whom the police had been put on a heightened state of alert, and in anticipation of whom Detective Sergeant Pete Rance had spent hour after "cold, mundane, boring" hour watching houses, post offices and streets. But it was.

Not everyone that the unit goes after is a murderer or a rapist. Poland supplies them with the most business; more than half of their extradition requests come from the Polish police. Rather wonderfully, they even have a special, scheduled, weekly flight that takes wanted men from Britain to Poland. The problem is it tends to be populated by people guilty of such scurrilous offences as being drunk on a bicycle or having possessed cannabis sometime in the early Noughties. Most go home, pay their fine, do their time, and then return to the UK, where they have, more often than not, set up their lives. Is it a waste of police hours? The officers working on the case weren't sure. Well, actually, I'm fairly certain they were – but couldn't really start voicing opinions on national TV.

And so, again, to The Shadow Line. In truth, I didn't want to go here but realised – alas, too late – that the rest of the DVDs the BBC had dispatched were, in fact, impossible. One, Business Nightmares with Evan Davis , because it was the wrong episode and the other, A303: Highway to the Sun, because the disk was faulty. Actually, I'm not too bothered about the former. But an hour-long documentary about a motorway! That would have been delicious. I know, at least, that I would have liked it. I drove along the A303 once (or, more accurately, was driven; that conspicuous badge of capability, the driver's licence, continues to elude me). And, yes, it was beautiful. So much nicer than the M4 and M5, with views of Stonehenge to boot.

But The Shadow Line, take three. So pleased with myself for actually being able to keep up with last week's plot, this time around I was utterly bemused. Jonah continued doing what he does best: forgetting things and being weird. I wouldn't trust him if I were Lia. On the other side of the law, gangland put on its best parade of Grizzled Geezers. They all look alike, more or less, which only adds to the sense of confusion. One thing, though, became clear: nice Mr Gatehouse isn't so nice at all. Well, I don't like him after he shot poor Andy.

a.jarvis@independent.co.uk; twitter.com/aliceazania