‘There’s another thing I’m worried about,’ Gerard said, looking at Georgia. ‘What if electronic countermeasures are deployed around the prime minster?’

Georgia looked thoughtful. ‘Jamming the control signal for our drone?’ she asked.

Gerard nodded as Zac, Elodie and Kamila looked concerned.

‘Is that likely?’ Zac asked.

‘I’m not an electronic security expert,’ Gerard said.

‘We could use the drone’s homing setting,’ Georgia suggested. ‘By default, the survey drone is programmed to pilot itself back to its launch point if it loses a control signal for more than a few seconds. But you can set the return point manually to anywhere you like …’

Gerard understood. ‘If we know where the prime minister will be standing, the drone will still go there if our signal is jammed.’

Georgia nodded. ‘There’s a Java programming interface. I’m no coder, but it should be possible to write a program that makes the drone trigger the impeller before an emergency landing.’

‘I did a ton of coding in my teens,’ Gerard told Georgia. ‘I can help you to figure it out, but we’ll need the precise location where the prime minster will be making his speech.’

‘Is that possible?’ Zac asked. ‘Without breaking in and measuring the building site.’

‘With a laser measure, an altitude reading and some very basic maths,’ Gerard said condescendingly.

‘Does this mean we don’t need to be at the scene?’ Kamila asked. ‘Can we hide the drone nearby the night before?’

Georgia shook her head. ‘It’s a back-up. It gives us a chance if they block my control signal. But we’re much more likely to hit if I’m piloting, rather than guessing where the prime minister will be in advance.’

When she got home from the Red Parrot, Georgia found her dad’s good Nikon camera, then fitted his longest zoom lens and put it on charge. Zac met her on the way to school the next morning, collecting the camera, then visiting Tower Fifty-Two with Elodie and taking photographs of Banque Générale’s building site.

First thing Saturday, Georgia left home before her dad woke and took the short walk to the workshop. Zac and Elodie had to work, but Gerard borrowed an ancient Volvo estate car from his grandad and they loaded it with the drone, an identical back-up drone and a rolling cabinet that Georgia had packed with batteries, tools and spare parts.

There was a tangerine sunrise as Kamila drove thirty miles north to a farm owned by one of Gerard’s work colleagues. Georgia had spent Friday afternoon’s double-history lesson writing a test-flight program worthy of NASA, and Gerard chose to be impressed rather than snarky.