'Okay, we're working on it, don't panic.'

'I know what they are,' said Maggie Armitage excitedly, flapping a ringed hand at the doctor, 'why won't anyone listen to me?'

'Sssh, I can't hear him very well.' Masters held his receiver closer.

'People don't listen to you, Margaret, because you get everything wrong,' Stanley Purbrick complained. 'You new age people are all the same with your lovely warm wibbly-wobbly vibrations and purple auras, but when it comes down to hard facts and figures you ignore the evidence. New age? Symptoms of old age, more like.'

'Oh, for the love of Mithras don't give us your government infiltration theories again,' complained Maggie. 'Call me narrow-minded but I think there's a bit of a difference between you insisting that Margaret Thatcher was involved in the cloning of Ronald Reagan's sperm to create a new breed of super-politicians, and my beliefs about astral alignment.'

'The main difference is that my theories are rooted in scientific reality and yours involve waving a bit of crystal about on a thong.'

'Your aura turns a very unpleasant shade of heliotrope when you start being rude, did you know that?'

'I wonder if you two could give it a rest for five minutes and help out here?' asked Jane Masters, pointing to her husband holding the telephone receiver.

Maggie pushed herself forward, elbowing Stanley away. 'They're crosses. Tell him they're all types of crosses. Heraldic ones, all kinds. There are drawings in this book, look.' She held the pages open for all to see. 'They're not just Christian, you know. The ancient Egyptians used them as sacred symbols. And the Aztecs.'

'There used to be a chocolate bar called an Aztec,' said Purbrick, morosely hoisting a bottle of red wine over his empty glass.

'Vince, we think they're crosses,' said Masters. 'Though I don't see a connection between such artefacts and the Anne Boleyn lines.'

'Suppose the lines were just there to point Vince towards Anne Boleyn,' said Jane.

'So what?' asked Purbrick. 'She's connected with all sorts of places.'

'Think about the crosses. Is there a particular church associated with her? What about the chapel at Hever Castle?'

'But that's not London, is it?' said Jane.

'Isn't there an exhibition at the National Portrait Gallery, something about the Treasures of Hever Castle? Paintings on loan.'

'Does anybody have a newspaper?' asked Arthur Bryant.

'There's one in the rack over there.'

Maggie tore open a copy of the Independent with a theatrical flourish and began intently scouring the pages, which was a waste of time because she was looking at the sports section, having left her reading glasses in a vegetarian restaurant in Tooting the night before. 'Nothing in here,' she concluded. 'Pass me the Guardian.'

But Masters had already found the appropriate advertisement. 'Here you are, "Treasures of Hever Castle", opening tomorrow at the National Portrait Gallery, and there's a reproduction of one of the pictures.'

'Oh, it's the famous one,' said Jane, 'the portrait of Anne Boleyn by Hans Holbein. That would fit the bill.'

'That's where you have to go,' Masters told Vince. 'Then I guess you need to find something with a lot of crucifixes.'

'It had better be on the outside of the building, or nearby. I certainly won't be able to get in.'

'Saint Martin in the Fields is opposite. Could that mean something?'

'No,' said Vince. 'This is something in or on a painting, I'm sure of it.' He knew how much Sebastian admired monarchist art. Holbein's portrait of Boleyn would have struck a chord with him. Perhaps he simply expected Vince to break a window and find the next letter before anyone could catch him, but such an attempt would be suicidal.

'Hang on a second.' The doctor turned to Purbrick. 'Who do we know at the National?'

'George Stokes has been there for over thirty years,' said the elderly gentleman who had just let himself in from the hall. 'A good man. Helped me sort out some nasty business with a vandalised Pre-Raphaelite a couple of years ago.'

'Do you have his home number?' Masters turned his attention back to the telephone. 'Listen Vince, this is going to take some organisation. If what you're being sent to retrieve is inside the gallery, we'd have to get the keys and the alarm codes for the entry system.'

'Is that possible?' asked Vince, his voice fuzzing as a truck passed.

'I wouldn't have thought so, but it's worth checking out. Head in that direction and we'll call you back.'

'Wait, you don't have my number.'

'Last number redial!' they exclaimed in unison.

'That's the trouble with young people today,' said Maggie Armitage, still trying to read the newspaper. 'They've a very poor grasp of modern technology.'

'Have I been missing something?' asked the frail elderly gentleman, unwinding a length of ratty red scarf from his throat. To those who did not know him well, Arthur Bryant was a cantankerous old tortoise who crept about the city in a rusty blue Mini Minor. He was two years past retirement age and capable of only the most rudimentary politeness to a handful of close acquaintances. Shunning technology, buried beneath scarves, forever complaining, he lived only for his investigative work at the North London Serious Crimes Division, housed above the tube station at Mornington Crescent.

As his commissions grew more prosaic and less taxing, he kept his agile brain alive by arguing with his partner John May, and by paying regular visits to Masters and his charming wife. For twenty years Bryant and May had shared an office at Bow Street police station before moving north, working the cases no one else wanted, and evolving some highly unorthodox methods. Their knowledge of London and its fringe elements was unique and indispensable, and gave them an advantage over younger officers.

'Arthur, you're late again,' the doctor pointed out. 'You were supposed to be here ages ago.'

'Oh, I had some difficulty with Bunthorne,' explained Bryant, rummaging around in the pockets of his voluminous tweed overcoat. A puzzled look crossed his wrinkled features for a moment, then he pulled a ginger cat from one of the pockets.

'What on earth have you got there?'

'Well, that was the problem with Bunthorne, you see. All this time I thought he was a tom, but tonight he wandered into my bedroom and rather unexpectedly produced four kittens. I had to leave Alma with them.'

'But that's not a new-born kitten,' said Maggie, pointing to the ginger cat that was now contentedly threading its way through the legs of the assembly.

'No, you're right there,' said Bryant vaguely. 'It's a stray I picked up on the way over. I had cats on the mind, and the snow was starting to turn to rain, and the little thing was shivering inside a scrap of binliner on Battersea Bridge. A bowl of warmed milk would probably please it, Jane. Then perhaps someone could explain what all the excitement's about.'