“Chronic, sir. Nothing much to do as a general rule except walk and think.”

“I know.”

Gratified by this encouragement, the constable said: “Yes, sir. I always reckon that if there’s any chap or female on this beat, hanging off and on, wondering whether they’ll make a hole in the river or not, it’s between two and four of the morning they’ll go overboard if they’re ever going. The river patrols say the same thing.”

“Yes,” said Alleyn. “So do doctors and nurses. It’s the hour of low vitality.” He did not move away and the constable, still further encouraged, continued the conversation.

“Have you ever read a play called ‘Macbeth,’ sir?” he asked.

“Yes,” said Alleyn, turning his head to look at the man.

“I wonder if it’d be the same thing, sir. The one I have in mind is by this Shakespeare.”

“I think it’ll be the same.”

“Well, sir, I saw that piece once at the old Vic. On duty there, sir, I was. It’s a funny kind of show. Not the type of entertainment that appeals to me as a general rule. Morbid. But it kind of caught my fancy and afterwards I got hold of a copy of the words and read them. There’s one or two bits I seem to be reminded of when I am on night duty. I don’t know why, I’m sure, because the play is a countrified affair. Blasted heaths and woods and so on.”

“And witches,” said Alleyn.