Every time these thoughts surfaced she pushed them back down, but they were persistent.

She almost preferred the Land Cruiser – until she recalled the pure, claustrophobic terror of that ordeal.

She was trying to work out what she knew.

She guessed that she and Martha had been brought aboard the boat at around 1 a.m., and she estimated that it was now somewhere around noon: some hours earlier, just before dawn, she had heard her captors perform their salat al-fajr prayers and had then watched as the hatch above her head was gradually revealed by a thin square of daylight.

She knew that the boat was moving – the rhythmic chugging of the engine and that gentle roll told her as much.

She did not know which way they were going, but common sense told her that it wasn’t west to the Atlantic, or back north to Spain; that meant they were almost certainly following the continental coastline, across the top of Morocco and over into Algerian waters.

She also didn’t know how far they’d gone. Her best guess was that they’d set out a dozen or so hours ago. She knew that a ship’s speed was measured in knots, but she had no idea what a knot was. So she tried to guess their speed in miles-per-hour. She came up with 12mph – another good guess.

Twelve hours and 12mph meant 144 miles.

She was only a little out. In fact, they were some thirty miles further on, just past the northern Algerian town of Mostaganem, fifteen miles off the coast and just outside that country’s territorial waters.

To her right, in the stinking gloom, she could see Martha, slumped on another steel chair, also cuffed, head down between her knees.

She hadn’t said a word for hours, and Charlotte was worried about her mental state.

But for now she put it behind her – she needed to conserve all her mental energy for herself.

In the dim light, she saw a loose nail sticking out of a wooden crate to her left.

She looked at the rusty steel hull behind her, and then back at the nail.

A thought had occurred to her.

She began trying to work the nail loose.

Fifteen feet above her head, Khasmohmad Kadyrov and Argun Shishani were sitting, under cover, in the wheelhouse – with the West’s satellites and spy planes, it was too risky for either man to show himself on deck in daylight unless absolutely necessary – and looking out at the wide blue Mediterranean.

It was another beautiful day.

‘So far, so good, brother,’ said Shishani.

‘It’s almost too easy,’ said Kadyrov. ‘But I don’t like being on this boat. Too slow. The sooner we get off it…’

‘How long to Tabarka?’

‘We’ll be there late tomorrow night, or early the next day. The British and the Americans will assume we are travelling by land, and will be watching the roads in Morocco. The Moroccans will have been alerted – they are in the pay of the West. So the sea is our friend.’