Jannika was still sitting, huddled, in one corner of the basket, with a blanket Müller had brought wrapped around her. But Tilsner had lifted Johannes up, so he could gaze in wonder at the scene below. They were drifting in and out of low cloud, but when it cleared the view was heart-stopping.

‘Look ahead,’ Tilsner pointed as he shouted. ‘Those lights down there. It’s the motorway crossing at Hirschberg. Those red lights are car tail lights.’

‘Wow!’ said Johannes. ‘They look just like toys.’

‘Then the row of yellowish lights facing us are the headlights of cars coming from the BRD. The line of more spaced out, whiter lights, at a ninety-degree angle to the autobahn, is the state border.’

Tilsner’s knowledge of geography had always been pretty poor, so Müller wasn’t entirely sure why she’d allowed him to become the navigator and pilot. But on this occasion, he seemed to know what he was talking about. She roused Jannika to come and take a look. The girl staggered over reluctantly, holding tight to the side rail.

‘Does that mean we’re going in the right direction?’ Müller shouted back, knowing they were high enough up for their voices not to carry to the border guards below. She wondered if their take-off site had been discovered yet. They’d deliberately started several kilometres back from the border to try to avoid detection.

Tilsner put Johannes down for a second, got out his pocket torch, and shone it on his map. ‘As far as I can work out, yes, we are. It shouldn’t be too much further. But I told you before, we can’t steer this thing. We’re at the mercy of the wind. If it takes us off course, all we can do is go higher or lower, and hope we pick up an air current going in a slightly different direction.’

For Müller, it meant too much trusting to luck. She knew she’d put herself – and her two children – in an impossibly dangerous situation.

But she’d been desperate. To save them, and herself.

Tilsner was still having to light the burner sporadically to ensure a level flight – something he’d explained to Müller was virtually impossible. It was simply a case of knowing when to heat up the air inside the envelope of material to slowly ascend. All the time the burner was off, they were slowly descending. Already, it seemed as though the motorway crossing point was behind them.

‘I’ll let it descend naturally in a few minutes,’ said Tilsner. ‘I just want to be certain we’re well into BRD territory – we probably already are.’