Even with (almost) all the evidence anybody could want.

It was a dispute between neighbours, something simple and stupid. A lawnmower that never got returned or someone complaining about a noisy party. I can’t remember the details of why they fell out, but several other neighbours told us they were aware of tensions, so we knew damn well they had. Our only suspect – a charmer of a long-distance lorry driver named Ralph Cox – lived in a house with a garden that backed on to the teacher’s. After one conversation with Mr Cox, despite him claiming that he’d been indoors all day, we were convinced that he’d marched round to Evans’s place to have it out and things had got out of hand.

Forty-two separate stab wounds out of hand.

Yeah, so this evidence . . .

Cell-site data meant we were able to place Cox’s mobile at the scene, but it was quickly pointed out that living within fifty yards of the victim’s property meant his phone would have been pinging off the same mast if he was at home. Marvellous. We had our suspect’s prints inside Evans’s house, but Cox’s claim that he had been there before to discuss the dispute – which to be fair he’d never denied – could not be disproved. We never found the murder weapon, but we had a knife-block from Cox’s kitchen that just happened to be missing a knife whose blade was the size and shape of the one that had sliced up Gordon Evans.

We had an eye witness, another neighbour, who said he saw Cox leaving Evans’s house on the afternoon in question. By the time we came to take a statement, though, that had become thought he saw, then I’m not actually sure it was him and eventually he made it clear that whatever he might or might not have seen, he wasn’t willing to talk about it in court. Yeah, Cox was a scary-looking sod and this witness only lived a few doors away, but still it was a pain in the arse.

Then there was the camera.

There was no CCTV on the street, but the neighbour opposite had a security camera that happened to cover Evans’s front door. You can see where this is going, right? A DVR that was full, so nothing recorded.

That just about put the tin lid on it.

All this, on top of which, Johnno and me were getting it in the neck from a useless DI who was desperate for a result and couldn’t understand why we weren’t delivering one.

So one night I went round to Johnno and Maggie’s place to talk about this case that was doing our heads in. We got Chinese and ate off our laps, the three of us just sitting round moaning about it.

What were we doing wrong? What weren’t we doing?