‘Okay, so…’ He turns to the whiteboard behind him, and draws a crude outline of the British Isles and the north of Europe. ‘From the beginning. The storm was caused by the Spanish Plume effect.’ He draws a series of arrows, moving up from the main body of Europe. ‘Hot, dry air moves north from Spain towards the UK. Since the Spanish interior is over 700 metres above sea level, this hot air acts like a lid, trapping the build-up of warm, moist air near the surface.’ He looks at Grey. ‘The loaded gun,’ he adds with a smile. ‘As it moves north, the elevated plume of hot air rises, begins to cool and forms cloud. This makes it unstable, creating storms that are made bigger by feeding off the warm, moist air trapped below.’ He draws another diagram with yet more arrows and what Robin assumes is a cloud. He feels sorry for the poor students in Calloway’s lectures if this is the quality of the teaching; he’s certainly none the wiser.

Calloway continues: ‘It means the warm, moist air near the surface needs to get strongly heated by the sun. It will then break the cap and release its energy as powerful thunderstorms.’

‘And this is common in the UK?’ Robin asks.

‘Once every two to three years? And we can only predict a few days ahead, so once we realised, it was all go.’

Robin accepts defeat on the technical explanation. Desperate to move onto simpler ground, he asks, ‘Could you show us his office?’

‘Sure.’ With a last caress of the satellite dish, Ian walks out of the lab and up the stairs at the back. They arrive at a row of standard-looking offices that wouldn’t seem out of place in a corporate headquarters, albeit a shabby one. He stops at the end, at a small, poky room with Dr F. Mason written on a piece of paper, crudely Blu-Tacked to the glass.

Ian pulls a key out of his pocket and opens the door. Robin walks inside.

‘Dr Mason’s a senior staff member, right?’ DC Grey asks, the two of them standing in the doorway. Calloway nods. ‘So why the small office?’

Ian laughs. ‘It’s the same one he was allocated when he first became a lecturer. He never moved.’

‘And you’re his PhD student?’

‘One of. Dr Mason has four. But I’m the one who works most closely with him on the radar.’

The office is as messy as Finn’s flat. Paper litters the floor, and the bin is full and overflowing. A row of stained coffee cups runs the length of the windowsill, next to a brown spider plant.

‘So why weren’t you there the night of the storm?’ Robin asks. He gets a look from Grey. Well, if you’re not going to ask, he thinks, with a glare back.