Luke looked at her with admiration. It was easy to forget on jobs like this that Jenny had been a scientist long before she became an intelligence officer. They were down in the basement, two floors underneath the lobby of the Vauxhall Cross headquarters of the Secret Intelligence Service, visiting the mysterious part of MI6 that did the gadgets and tech. Luke remembered his uncle telling him that Q Branch had not always been called that. It used to be known as ‘TOS’, short for Technical Operational Services, until its boss complained that his team were fed up with being called ‘Tossers’.

Now, with the Moscow mission looming within hours, a decision had been taken at the highest level to give Luke and Jenny a crash course in the very latest advances in encrypted communications.

‘Quantum key distribution is a lot to take in so I’ll try to keep this simple,’ the man from Q Branch pressed on.

Please do, Luke thought, as he sensed he’d be well out of his depth in the next few minutes.

‘So,’ continued the boffin, warming to his subject now, ‘even though you’ll be working in tandem with our Russian “friends”, make no mistake. They’re going to be all over your comms like a rash. We can expect all three of their intelligence agencies – the GRU, the FSB and the SVR – to be doing their damnedest to get inside your devices and intercept every byte of data you send back. So how should you communicate securely? I’m going to show you.’

He took a couple of paces over to the white workbench next to him and picked up a smooth, flat object. ‘Looks just like an ordinary smartphone, right?’ He answered his own question with a knowing shake of his head and a waggle of his finger. ‘Well, it isn’t. This beauty is your transmitter. Not long ago it would have been about the size of a traditional stereo music amplifier, the sort of thing we had in our bedsits when I was growing up. But now, with a bit of input from the private sector, we’ve been making great strides in miniaturization these days. And this little baby will send—’

‘An encrypted beam of photons?’ Jenny cut in.

‘Exactly! And they can only be decrypted by the receiver, which we operate.’

‘But doesn’t that require a fibre-optic cable?’ Jenny said. ‘You’re not going to tell me we’re using the Russian grid?’

The man from Q Branch gave a great belly-laugh, as if this was the best joke he’d heard in ages. ‘No, that wouldn’t be wise. Instead,’ he held up a finger, pointing towards the ceiling, ‘we use a low-orbiting satellite. The beam of photons will go straight up from your device into space, where it’s picked up and bounced back to Earth, where our people then decode it using the same random key.’