At Dick’s wharf Ali had checked the control rooms at the stern of each of the six barges twice. When the convoy sailed on its last voyage he would be on barge number five, the barge which would destroy Chelsea Bridge. He would be in constant radio communication with all the other barges. He also had a small TV set in the control room of that barge. He would see the BBC broadcast the frightful destruction he would wreak.

Bridges smashed, the Thames full of cars and other traffic which had fallen into the river, crammed with people -either already dead or the few who would drown. It would be high tide. For years North London would be severed from the south. But it was the thousands of casualties he looked forward most to seeing.

He descended to the interior where all his cell was assembled. They were kneeling on their prayer-mats, facing east. They rose up slowly as Ali stood on a crate to address them in Arabic.

‘Allah is great,’ he began. ‘Allah is looking down on us to see our work on his behalf. You will all carry explosives strapped to your bodies. The enemy will also be driving along both sides of the river bank, on their way home. Their last drive. You know what to do? To those who survive?’

‘We know,’ one huge Saudi called out. ‘We get into the craft and speed to the shores…’

Ali had been meticulous in checking motor-powered dinghies were arranged along the roll-over decks. His cell had forty men and he felt sure a large number would survive long enough to arrive on the embankments. Once there they would use their sub-machine guns to spray the slow-moving traffic.

‘Then,’ the Saudi continued, ‘we slaughter as many infidels as we can before we rush at crowds of pedestrians, clasp them and detonate our bombs. The Embankment will flow with their blood.’

There were shouts of praise from the packed cell, standing in rows behind each other. Ali raised a hand and the shouts ceased. It was not that he didn’t approve of their reaction. Ever cautious, he didn’t think there was any risk of their shouts being heard in the nearby hospital, not with the main hatch being still closed, but he couldn’t risk it. Below the closed hatch was a roped-off area. Inside it perched the first of six torpedo shells, crammed with explosive, aimed to pass easily through the main hatch and then strike the central span. Beside it stood two men – one to press the button to activate the bomb, the second man to press the button which would send it winging its way upwards.

Ali, very athletic, shinned up the ladder (soon to be removed) and ran along the deck to the bows. Here they had placed a smaller bomb, the barrel of the launcher angled. This would be fired as soon as Nebuchadnezzar, the name of the main bomb, had been sent on its terrible way.

The smaller bomb at the bows would be aimed at the support struts of the bridge, to ensure the entire bridge collapsed. It was a refinement aboard all six barges – and something the defenders on the river banks were unaware of.