Derek Heaton, it emerges, walked into a packed Birmingham mosque on a Saturday morning in January, pulled a shotgun that he legitimately owned from a guitar case and fired at the worshippers. For several minutes, he stood alone, snapping open his weapon and reloading every two shots, picking off anybody who didn’t escape in time or hide successfully. Four of his victims died and between ten and twenty more were injured – the class struggle to settle on a figure on which they agree. Armed police arrived but Heaton refused to drop the gun. Instead, he pointed it at them. In the space of less than a second, eight rounds peppered his body. The term ‘suicide by cop’ is bandied round the room.

‘So we all understand the incident,’ Mr Clark says. ‘But do we understand the why?’

‘He’s a fucking nutter,’ Joey Mackie contributes.

‘Anybody got something more constructive for me?’ Mr Clark asks. ‘What do we know of this man’s history?’

Amit and Lei Pang wade into the discussion. A picture builds of a middle-aged man, once a successful business owner in the area. He attributed the failure of his wholesale grocer’s to unfair competition from the large local Asian community. Unemployed and in financial crisis, his life remained outwardly normal. His wife claims their marriage was still happy; neighbours spoke of a man who was friendly and went out of his way to help. But it’s since emerged that he was living a double life. Historically an outspoken liberal, he developed an interest in far-right politics. It began with joining marches, in assuming a new and narrow circle of friends. It ended in a bloodbath.

The class are shouting over each other, chiming in with opinions. But from the white noise there are certain words that project clearly through the static, clipped and clear each time they’re uttered.

‘Atrocity.’

‘Terrorism.’

‘Mass murder.’

They prick at me, penetrating the invisible partition that encloses me and what lies concealed at my feet. They’re familiar words: ones I find in my head when I jolt awake from a precious hour or two of sleep, that illuminate like neon lights to terminate those rare and careless moments of thinking about something other than this day.

A palm is waved in front of my face. ‘Are we boring you?’ Mr Clark asks.

There are a couple of ‘Mooor-coombe’ howls, but they don’t catch on, the volume never reaching the feedback screech it usually does.

‘So, Ollie, what are your thoughts on Derek Heaton’s motivations?’ he asks me.

It takes me a moment to reassemble the discussion. ‘He’s evil, sir.’

He nods, looking half impressed that I’ve offered anything at all. ‘Why choose the word evil?’

‘He murdered innocent people.’