‘The level of resolution. And the algorithm Dr Mason developed means the data returning can be translated into a much more detailed backscatter image.’

‘And why is that important?’ Robin says, still baffled. He knows he’s supposed to be a silent observer, but his police inquisitiveness is ingrained.

Calloway takes the question in his stride. ‘The greater the detail, the better we can know what’s coming. Rain, hail, snow, ice. Tornadoes.’ He smiles. ‘It saves lives. But not just that – it has incredible commercial applications, too. Hail destroys millions of dollars’ worth of crops every year. It decimates solar panels. Being able to forecast this stuff means companies can save a huge amount of money. Insurance companies will love it.’ He pauses. ‘Do you know when we’ll get the equipment back from the van?’

‘It’s going to take some time, I’m sorry,’ Grey replies. ‘How did the BBC fit into all of this?’

‘Dr Sharp’s an alumnus here, he did his doctorate alongside Finn. He’s quite a celebrity, so when he got in touch, we were all excited.’ Ian sits back on one of the stools, warming to his explanation. ‘He particularly mentioned the Doppler, saying they wanted to try something new, showcase new technology, and asked whether Dr Mason would work with them.’

‘Sophie said Finn was reluctant at first?’

‘Yes, we couldn’t understand it. But once Finn realised what it could mean for our funding, he quickly came around. You saw that van?’ Robin and Grey both nod. ‘Custom-made, specially adapted so it could fit up into the car park. Finn would have sat there in his Ford Focus, given half the chance, but Sharp only wanted the best. Needed to look good on TV.’ Calloway grins happily. ‘And we didn’t complain.’

Mystery solved, Robin thinks. Although it still must have been close, barely squeaking through the maximum headroom of the multistorey.

‘And the storm was a loaded-gun scenario, right?’ Grey asks, and Robin looks from the DC to Calloway, confused.

‘That’s right,’ Ian confirms. ‘You know your storms.’ Grey smiles back.

‘Explain?’ Robin asks, bluntly.

Calloway turns to him. ‘How much do you know about thunderstorms?’

‘Nothing.’