William thought as he so often did, about his mentor, Constable Fred Yates, who had saved his life only to sacrifice his own. Police work wasn’t always as romantic as some authors would have you believe. He moved quickly on. ‘What book am I reading?’

‘Watership Down by Richard Adams. And before you ask, you’re on page hundred and forty-three.’

‘And my clothes, what do they tell you?’

‘I admit,’ said James, ‘I found that a bit of a mystery. It would take me several subtle questions before I came up with an answer, and then only if you told the truth.’

‘Let’s assume I’m a criminal who won’t answer your questions until I’ve phoned my legal representative.’

James hesitated for a moment before he said, ‘That in itself would be a clue.’

‘Why?’

‘It would suggest you’ve been in trouble with the law before, and if you know the telephone number of your lawyer, you certainly have.’

‘OK. Let’s assume I don’t have a lawyer, but I’ve watched enough TV programmes to know I needn’t answer any of your questions. What have you been able to work out without asking me any questions?’

‘Your clothes aren’t expensive, probably bought off the rack, yet you’re travelling first class.’

‘What do you deduce from that?’

‘You’re wearing a wedding ring, so you could have a rich wife. Or perhaps you’re on a special assignment.’

‘Neither,’ said William. ‘That’s where observation ends, and detection begins. But not bad.’

The young man opened his eyes and smiled. ‘My turn, I think, sir. Please close your eyes.’

William looked surprised, but continued with the game.

‘Describe me.’

‘Bright, self-assured, but insecure.’

‘Insecure?’

‘You may be top of the class, but you’re still desperate to impress.’

‘What am I wearing?’ asked James.

‘A white button-down cotton shirt, possibly Brooks Brothers. Dark blue shorts, white cotton socks and Puma trainers, though you rarely, if ever, visit a gym.’

‘How can you be sure of that?’

‘I noticed when you walked towards me that your feet were splayed. If you were an athlete, they’d be in a straight line. If you doubt me, check the footprints of an Olympic runner on a cinder track.’

‘Any distinguishing marks?’

‘You have a tiny birthmark just below your left ear that you’ve tried to hide by growing your hair, although that will have to be cut short when you join the FBI.’

‘Describe the picture behind me.’

‘A black and white photo of this ship, the Alden, sailing out of New York harbour on May twenty-third, 1977. It’s being accompanied by a flotilla, which suggests it was on its maiden voyage.’

‘Why’s it named the Alden?’

‘That isn’t a test of observation,’ said William, ‘but of knowledge. If I needed to know the answer to that question, I could always find out later. First impressions are often misleading, so assume nothing. But if I had to guess, and you shouldn’t as a detective, as this ship is part of the Pilgrim Line, I’d say that Alden was the name of one of the original pilgrims who set sail from Plymouth to America on the Mayflower in 1620.’