'I honestly don't know,' Hasim said. 'He only mentioned the name Al Qaeda once, like I told you, when he sentenced me to death.' And then he frowned. 'I think he takes his religion seriously.'

'In what way?' Billy asked.

'He paid me and my friends once to smash up a shop selling anti-Muslim literature; then on another occasion to do the same to a place selling pornographic magazines.'

'Did you do that often?' Billy asked.

'We torched an old shop somebody had bought with the intention of turning it into a massage parlour. He told me over the phone that the people involved used young girls and that his boss thought it an offence against Allah.'

'Well, I agree with him there,' Harry said. 'But who was this boss he mentioned?'

'I haven't the slightest idea,' Hasim said. 'That was the only time he said such a thing.'

Harry turned to Billy. 'What do you make of this?'

'It fits with the Al Qaeda attitude,' Billy told him. 'They follow the teachings of the Koran, they're moralists, and these joints Hasim and his pals turned over were purveyors of filth.'

'All very well, my old son, but the attack on the Dark Man was nothing to do with Allah or the Koran, and everything to do with some personal vendetta against all of us,' Harry said.

'I agree,' Billy told him.

'Then I suggest you do something about it, like getting your arse over to Tangier Wharf, grabbing Lancy by the scruff of his neck and bringing him back here where I can put a few pertinent questions to him.' Harry looked grim. 'I mean, Muslim morality is one thing, but he's got questions to answer. Take the boys as backup if you want.'

Billy nodded to Baxter. 'I'll take Joe as driver, and Hasim might be useful. I'm just going to check my laptop. Roper was putting an identity photo through from army records.'

Harry said to Hasim, 'Do you feel okay about this? He sounds like a bad bastard.'

'Yes, I think he is.' Hasim looked tired, but shrugged and tried to smile. 'It's as Allah wills, Mr Salter. I made a bad mistake getting involved with this man. I will do anything to get rid of him.'

Billy returned wearing a dark single-breasted raincoat. He produced a silenced Walther from the interior pocket, checked it and replaced it.

He said to Baxter, 'You tooled up, Joe?'

'In the car,' Baxter told him. 'A selection.'

'That's it then.' Billy put a hand on Hasim's shoulder. 'Let's get it done.' Selim Lancy had been visiting his mother in the oncology department at St Luke's. An operation for her skin cancer seemed to be working and they'd assured him the treatment had stopped the spread. He'd taken her flowers and sat with her for a while. She was a kind and simple person who divided her time between keeping the old Victorian flat on Tangier Wharf spotless and offering whatever services were required at the mosque.

She was overwhelmed by what seemed to her the luxury of her private room at the hospital, and Lancy had spent time assuring her that they could afford it. Except for pocket money, he'd always put everything into her deposit account, including the largesse from the Preacher, a total in excess of fifty thousand pounds. The dangerous game he had chosen to play carried the chance of instant death at any time, so it was his way of making things as simple as possible by leaving her everything in advance.

When he'd had enough, he kissed her hand and said to her in Arabic, 'Sleep well, Mother, Allah and all the angels protect you.'

Her eyes already closing, she murmured something and he eased out. Turning from the busy right lane traffic of Wapping High Street into the gloom of Tangier Street was like a journey back in time, the old warehouse buildings, several storeys high, rearing up into the night, obviously waiting for the developer.

The streetlights were museum pieces, many of them originally gas lamps from the look of them. There was a strange, brooding air to the place, as if it was waiting for something to happen, as Joe Baxter cut his engine and coasted down over the cobbles to the Thames below.

'What a bleeding place to live,' Billy said. 'You'd only need the cameras to make a Jack the Ripper film.'

'It gives me the creeps,' Hasim said. 'I'm already imagining a bogey man waiting to jump out at me.'

They coasted silently down to a Victorian tower-like rookery about five storeys high, the wharf below it creating a basin of deep water where ship and barge traffic had been able to ply their trade. A gateway, its gates long gone, gave entrance to a courtyard, and the only light came from a lamp bracketed over the main door. A rotting sign said: 'Tangier Wharf, Hart amp; Son, General Shipping, 1852'.

'Christ,' Billy said. 'It's like Charles Dickens is writing the script.'

There was a modern sign at one side of the entrance, advertising a development of apartments and offices the following year with unsurpassed river frontage.

'I don't care what they do,' Hasim said, 'this place would still give me the creeps.'

'Never mind that,' Billy said. 'The important thing is there's no sign of a silver Mercedes in the courtyard, so we'll go and suss out the situation. Joe, just put the car across the street in that turning, so that it's out of sight.' Baxter switched on for a moment and turned into the yard across the way, then killed his engine again.

Billy opened the glove compartment and took out a Smith amp; Wesson revolver. 'Have you ever fired one of these?'

'Never,' Hasim said.

'Well, you've been to the movies, so you know what to do.' Billy replaced the weapon in the glove compartment. 'You know where it is if you need it. Stay here and keep your eyes open. We'll check where he lives.'

They moved across to the courtyard and Baxter tried the front door, which swung open. There was a tenant listing beside the door, most of the slots blank, and Billy read it quickly.

'They've all gone, except for Mrs Lancy. She's on the top floor.'

'And she's in the hospital, isn't she?' Baxter said.

'She certainly is, so let's get up there and see if we can arrange a surprise for her son when he returns home.' Hasim sat there, not enjoying himself at all. The whole atmosphere of the place was threatening, and sitting in the Mercedes he felt claustrophobic, so he took the Smith amp; Wesson from the glove compartment, opened the door, got out and stood looking down at the river. A boat passed, lit up, the sound of people and music echoing across the water, and then the muzzle of a pistol was rammed into the side of his head and the Smith amp; Wesson torn from his hand.

'Now then, you young bastard,' Selim Lancy said. 'Let's have some answers. What the hell is going on here? Don't try lying to me. I know who Salter is, and I recognize the geezer with him from my visit to the Dark Man when you dropped me in it. You've been doing it again.'

'Come off it,' Hasim said. 'I didn't know your name, never mind your address, until they picked me up.'

'And how did they know where to find you?'

'Salter had a look at my Social Security card when they turned me over that night at the Dark Man.'

'And how do they know about me?'

'Salter said he had one of his men follow me a couple of times and he noticed you in the silver Mercedes. He thought it odd, so they checked your licence plate number.'

'So what are they up to now?' The muzzle of the gun bored painfully into Hasim's right ear.

'Checking on your place to see if you're at home. He said your mother was in the hospital.'

The fact that they knew about his mother disturbed Lancy and made him angry. 'The bastards,' he said. 'Bringing my mother into it. Well, we'll see if I can provide a nice surprise. Get moving, across the courtyard and straight down the left side and round the back.'

Hasim did as he was told, wondering what had gone wrong. It was, in fact, very simple. Lancy parked in a yard on the high street by arrangement with a shopkeeper. It was sheer chance that he'd walked down Tangier Street just after Baxter's silent approach and had – from the shadows – witnessed what had gone on.