TV police shows are either madcap comedies, gritty dramas or reality programmes with daft titles like Real Motorway Cops Undercover.

Babylon isn't any of these things. It's a mix of drama and comedy, so maybe you could call it a dramedy, or a comma. But there's also an element of the documentary about it, so maybe it's a comumentary. Who can say? All I know is it's very fast, clever and witty but, whatever label you attach to it, it's ultimately unsatisfying.

And I can't pinpoint where my sense of dissatisfaction comes from. I enjoy Babylon, but I don't love it. I certainly hope I never miss an episode, but not to the extent that I'll carefully set it to record. The characters are all well-drawn but I can never quite remember their names (except, of course, James Nesbitt, but that's because he's quite ubiquitous just now. But wait, his character isn't actually called James Nesbitt, is it? He's called…thingmy. The boss guy. The Commissioner.)

So if James Nesbitt was the most memorable thing about Babylon are they not in trouble, as they've just gone and killed his character off. In tonight's episode the news came through that his body had been found in the Thames. I kept waiting for the twist or the mistake or the cop-out of it all being a dream but, no, it was real. Richard was really dead.

His eminent colleagues displayed suitable shock and silence, but the rowdy coppers on the beat were less respectful, wondering if he'd killed himself because he'd messed up their pensions or if he maybe felt guilty about the recent bombings. Perhaps he'd been poisoned by the Russians or had taken part in a drunken dare to swim the river? As the news of his many extra-marital affairs broke, one of the cops wondered 'why would someone with so many birds want to kill themselves?'

Liz is employed to portray the police in a softer, more tolerant light, and the varied police reactions to Richard's death represented the job she has to do: decorum and dignity on the outside, with crude jokes and ugliness behind the scenes.

As well as breaking the shock news of the Commissioner's death, more PR trouble for the police arose when the armed unit were called to a late-night rave where it'd been reported that someone was waving a gun. In amongst the noise and flashing lights the police see the suspect raise his hand and they shoot. Of course, the boy - a young, black boy - was only raising his hand to gesticulate. There was no gun in his hand, but the police silently move one from his waistband to his rapidly-cooling palm, then meet in a seedy pub to get their story straight.

From witty one-liners to dead teenagers, jumping from comedy to drama and back again. Babylon can do both, but can only do them one at a time. There is never the seamless, luxuriant feel that both strands are running together and complementing one another, and so there's always the niggling sense of dissatisfaction. That lop-sided feel can only get worse now The Commissioner is dead.