Glenn thought hard back to his time on board the Scoob-Eee. There was a small cabin at the front that you accessed via steps, where the toilet, kitchenette and seating area were. When he had been down there, he had the impression it was mostly below the waterline. But if Jim Towers had been driving the boat, he would have been up on deck, in the partially covered wheel-house area. And if he was heading out to sea, there would have been a direct line-of-sight behind him to the shore. He explained this to Packham.

‘Super!’ he said. ‘Do you know if he made any calls?’

‘He didn’t bell his wife. I don’t know if he called anyone else.’

‘You’d need to get access to the mobile phone records. On a major crime investigation, that shouldn’t be a problem. I take it this is connected to Operation Neptune?’

‘It’s one of my lines of enquiry.’

‘So here’s the thing. If on standby, a mobile phone registers with its network every twenty minutes or so – it sort of checks in, saying, Here I am, chaps! If you’ve ever left your phone lying near your car radio you can sometimes hear that beeditty-beeditty-beep noise as interference with the radio, yes?’

Branson nodded.

‘That’s when it’s radioing in!’ Packham beamed, as if the sound was a trick he had taught all phones to perform. ‘Now, from the records, you could work out where the last registration occurred, to within a few hundred yards.’

He glanced around, conscious that almost everyone had now gone into the briefing room.

‘It would probably be in contact with, say, two or three coastal base stations and would be talking to a known sector, about a third of the circle on each.’

He glanced around again.

‘Very quickly, there is a thing called timing advance. Without getting too technical, the signal travels to and from the base station at the speed of light – three hundred thousand kilometres per second. That timing advance – depending on which network we are talking about – allows you to calculate a distance to the phone from each base station. Are you still with me?’

Glenn nodded.

‘Thus you have some approximate bearings – but, more importantly, distances from each, which together should allow you to triangulate a location within a few hundred yards. But you have to remember, this is only the place where the last registration took place. The boat could have moved twenty minutes on.’

‘So at least I would get its last known position and roughly the course it was steering?’

‘Spot on!’

‘You’re a star, Ray!’ Glenn said, writing down notes on his pad. ‘You’re a fucking star!’

At half past eight in the morning, two people, looking to the outside world like a mother and son, stood in line at one of the dozen EU Passport Holders immigration queues at Gatwick Airport.

The woman was a confident, statuesque blonde in her forties, with hair just off her shoulders in a chic, modern style. She wore a fur-trimmed, black suede coat and matching boots, and towed behind her a Gucci overnight bag on wheels. The boy was a bewildered-looking teenager. He was thin, with ruffled black hair cut short, and with a hint of Romany in his features, dressed in a denim jacket that looked too big for him, crisp blue jeans and brand-new trainers with the laces trailing loose. He carried nothing, except a small electronic game he had been given to occupy him, and the hope in his heart that soon, hopefully this morning, he would be reunited with the only person he had ever loved.

The woman made a series of phone calls in a language the boy did not speak, German, he presumed, while he played with his game, but he was bored with it. Bored with the travelling. Hoping against hope the journey would soon be over.

Finally, it was their turn next. A businessman in front handed his passport to the female, Indian-looking immigration officer, who scanned it, looking faintly bored, as if she was coming to the end of a long shift, and handed it back to him.

Marlene Hartmann stepped forwards, squeezed the boy’s hand, her leather gloves masking the clamminess of her own hands, then handed over the two passports.

The officer scanned Marlene’s first, looked at the screen, which flagged up nothing, and then scanned the boy’s. Rares Hartmann. Nothing. She handed the passports back.

Outside, in the Arrivals hall, among the plethora of drivers holding up printed or handwritten name-boards, and anxious relatives scanning everyone coming through the door, Marlene spotted Vlad Cosmescu.

They greeted each other with a formal handshake. Then she turned to the boy, who had never been outside of Bucharest in his life and was looking even more bewildered now.

‘Rares. This is Uncle Vlad. He will look after you.’

Cosmescu greeted the boy with a handshake and, in his native Romanian tongue, told him he was happy to welcome him to England. The boy mumbled a reply that he was happy to be here and hoped to see his girlfriend, Ilinca, soon – this morning?

Cosmescu assured him Ilinca was waiting for him and longing to see him. They were going to drop Frau Hartmann off, then go on to see Ilinca.

The boy’s eyes lit up and, for the first time in a long time, he smiled.

Five minutes later, the brown Mercedes, with grubby little buck-toothed Grigore at the wheel, pulled out of Gatwick Airport and on to the link road to the M23 motorway. Minutes later they were heading south towards the city of Brighton and Hove. Marlene Hartmann sat in the front passenger seat. Rares sat quietly in the back. This was the start of his new life and he was excited. But more than anything, he could scarcely wait to see Ilinca again.

It had only been a few weeks since they parted company, in a flurry of kisses and promises and tears. And less than a couple of months since this angel, Marlene, had come into their lives to rescue them.

It felt like a dream.

His real name was Rares Petre Florescu and he was sixteen years old. Some time back, he could not remember exactly when but it was shortly after his seventh birthday, his mother had run away from his father, who drank and hit her constantly, taking him with her. Then she had met another man. This man did not want a family, she had explained sadly to Rares, so she was putting him in a home where he would have lots of friends, and would be with people who loved and cared for him.

Two weeks later a silent old woman, with a face as flat and hard as a steam iron, led him up four flights of stone stairs, into a crowded, flea-infested dormitory. His mother was wrong. No one loved or cared for him there, and at first he was bullied. But eventually he made friends with other children his own age, though never with older boys, who regularly beat him up.

Life was hell. Early every morning they were forced to sing national songs, and like all the others, boys and girls, if he did not stand up straight, he was beaten. When he was ten he started wetting his bed and was beaten regularly for that. Gradually, he learned to steal from some of the older boys, who seemed to be able to get extra food. One day he was caught with two chocolate bars he had taken.

To escape retribution, he ran away. And stayed away, joining a community who hung out at Bucharest’s main railway station, Gara de Nord, begging and doing drugs. They slept wherever they could, sometimes in doorways, sometimes in tiny one-room shacks built along the overland steam pipes, and sometimes in cavities beneath the roads.

It was meeting pretty, lost Ilinca, in a hole beneath the road when he was fourteen, that had brought Rares alive for the first time. She had given him a reason to go on living.

Dragging their bedding further up the tunnel beneath the hot pipeline, away from their friends, they made love and they dreamed.