It was a violent place in which to discover a purpose. It was a good place to forge a friendship.

May felt exhilarated around Bryant. He had always imagined that somewhere out there, away from suburban dullness, ardent young people were allowed to give freer rein to their thoughts. He felt as though he had arrived at a place he had always wanted to be.

Do you enjoy reading?’ ‘I enjoyed Fifty Shades of Grey.’ Bryant quailed at the thought. ‘That’s not really reading, is it? More like staring at an assortment of words.’ ‘It is very popular.’ ‘So is taking photographs of your dinner for Facebook, but that doesn’t mean it adds to the total sum of human knowledge.

There are always regrets, of course. But you have to try and make a difference without hurting anyone along the way, so that you can reach a final state of grace without shame.

Now, the tourist hot spots of the city were the very parts that made it like everywhere else. Was it possible to imagine those buildings without inhaling the animal-fat stink of McDonald’s or KFC? He never thought London would cease to appeal to him, but the little faded glory it still possessed was being scuffed away by the dead hand of globalization. On his down days he saw London as a crumbling ancient house, slowly collapsing under the weight of its own past.

I’m not working class anymore,′ he said. ‘I’m lower-middle. I use three types of oil in my kitchen. Admittedly one of them is WD-40, but that counts, doesn’t it?

Tremble had a secret. Underneath his dreary exterior, he was quite interesting. When his penchant for investigating the area’s past was indulged, a light shown in his eyes and he became almost passionate, which is why his wife kept a stack of local history books on her bedside table.

If the killer had really wanted to keep his victim’s provenance hidden, he would have taken the head far away, or simply weighted it and thrown it into the fast-flowing tide of the Thames. The invention of the garbage bag had been a boon to murderers everywhere.

No more sending your clothes over to forensics to be dry-cleaned, no more running up kebab tabs on stakeouts and no more pawning items from the Evidence Room until payday.

We spend our youth attempting to change the future, he explained, and the rest of our lives trying to preserve the past.