On the other side of the road there was nothing, just a piece of wasteground and rows of blackened railway arches leading south out of the city. Here a number of raucous nightclubs were buried, and lines of clubbers, oblivious to the freezing night air, shuffled patiently forward in their black nylon puffa-jackets like war babies queuing for rations.

There had to be something else here.

…Pray Remember The 25th Of July…

What could that mean? Pray remember? Something to do with a church? The only other structure in sight was the cabbies' tea-stall he had sometimes used coming back from the clubs. That couldn't be it, could it? He carefully crossed the six-lane road, passing beneath the traffic cameras, and checked the walls of the shuttered plywood tea-cabin, but found nothing. The stall was closed for the night and there was little else of interest around. At least, nothing opposite the government building. The snow was growing heavier, speckling yellow in the lamps of Vauxhall Bridge. Vince looked at his shaking hands and knew that he would have to find a warm shelter soon. He dug into his duffel bag and pulled out a small diary. Flicking to July the 25th, he checked beneath the date. St James's Day. He knew nothing about the saints; his family were Church of England, and Vince considered himself an agnostic.

He would have to make another phone call. Part of him considered it cheating. On the other hand, if he was supposed to be, as Sebastian put it, 'a child of the streets versus the people who own the houses', he was free to decide that their rules were not his, and take the course he felt necessary. He reached the public call boxes beside Vauxhall station and punched out Harold Masters's number once more. The doctor answered on the third ring, almost as if he was expecting him.

'I'm sorry, Doc, I need your help again.' His breath formed over the mouthpiece. 'I hope I didn't wake you.'

'Oh, no chance of that. When you get to my age you sleep less. You don't want to risk missing anything. I felt you might ring again, and made according arrangements. We're going to be up all night.'

Thank God for that, he thought. 'It's a date – the 25th of July. Does that mean anything to you?'

'Well, it could mean all sorts of things. It really depends on which year.'

He hoped the doctor would keep his answers succinct. After this call, he only had twenty pence left in telephone change and would have to rely entirely on the mobile. 'St James's Day,' he prompted. 'Ring any bells?'

'No, not really. I have a Book of Days here, somewhere, perhaps that can -'

'Doctor, I don't have much time left on this phone. The clue says: "Pray remember the 25th of July".'

'That's the whole thing?'

'I'm afraid so.'

'Pray remember – wait a minute, would you?' There followed the sound of him setting the receiver down.

Shit, he thought, he's wandered off to ask somebody else and I don't have time for this. He heard the receiver being raised once more.

'You're in luck. I've brought in some friends. We're all in different academic fields, we just meet informally in a group, for the fun of it really. I thought they might be useful -'

'Doctor,' he cautioned. 'Time.'

'Yes, sorry. There's a tendency to ramble when one grows older. We think it was a street cry.'

'What was?'

'The "Pray remember" part, someone here says, hang on -' Vince could hear someone speaking in the background.

'Hello? Young man?' A new voice now, the voice of a middle-aged woman. The doctor was putting his friends on the line for a chat, for God's sake.

'Yes, I'm here.'

'I don't know if this is of any help at all, but in Victorian times, if you couldn't afford a pilgrimage to the shrine of St James on July the 25th, you built your own.'

'Hang on a sec,' said Vince, dropping his last coin into the phone slot. 'Sorry.'

'Are you still there? On St James's Day the poor children collected pebbles, flowers, shells and bits of pottery, and built little grottoes. They'd sit beside them collecting coins in their caps, and they'd call out "Pray remember the grotto". You heard the cry in the poorer parts of London as late as the 1920s. My grandmother can remember…'

Vince leaned out from the station alcove and peered back at the clubs tucked beneath the railway arches. The twisted rope of crimson letters jumped out of the gloom even at this distance. There must have been a hundred and fifty people queuing to get into The Grotto.

'Young man? Can you hear me?'

'Yes, I can, you've been a great help, thank you. And thank Doctor Masters for me.'

'He says you must call whenever you need him, no matter how late it is. He suffers from insomnia. We all do.'

'Thanks. I may well have to call again.' The Grotto. Very funny. Another of the League's little jokes. The club shared its name with one of the largest social organisations associated with the Freemasons. He returned the receiver to its perch and ran off towards the club.

Pam had followed her quarry to Cheyne Walk. This was quite the bravest and most foolhardy thing she had ever done. Behind her, the lights of Chelsea Bridge wavered in the falling snow, glittering in the icy river like the illuminations of an abandoned carnival. At the end of the street, the striding figure turned and crossed the junction into another road. She followed as quickly and quietly as she could. She was fairly certain that he had not spotted her; she had been careful to keep her distance for the last half-hour.

Pam presumed they were moving parallel to the river, but within minutes she was lost in the labyrinth of neat little streets. The buildings here sported an air of wealthy discretion. It was the sort of area where Members of Parliament were caught for drunk driving after visiting their mistresses.

The figure before her suddenly left the street, pushing open a high gate of black wrought iron. She was surprised to see a tall gothic building with mullioned windows set back from the pavement beyond a grass-covered quadrangle. She caught the gate with her foot just before it shut and slipped inside. He was stamping the snow from his shoes on the steps of the main entrance, muttering to himself. She waited on the far side of the flagstone courtyard while he twisted the door-ring and vanished within.

Pam waited a full five minutes before wobbling across the courtyard on her heels and standing before the bevelled iron ring. There was nothing she had covered in her business courses to account for this situation. She wished Vince was here. After a moment of hesitation she turned the handle and felt the door shift inwards, unlocked. Pushing it further open she saw a gloomy flagstone hall, a great oak staircase lined with unfurled flags – and half a dozen men in dinner jackets waiting for her to step inside.

Before she could back out, Barwick stepped forward and pushed the door shut.

'I'm glad you finally decided to join us,' said Sebastian. 'We were freezing our parts off waiting for you to make up your bloody mind.'