“Yes, I know who was on duty here that night. There was Bill Adams and Tom Short down by Whitehall, and there was George Mulligan patrolling up there by the Gallery. But it’s a hundred to one against any of them having noticed your man. Adams is on duty here, and the other two will be along at the station. You can have a word with Adams now, and I’ll take you along to the station myself in a few minutes. They’re just finishing up there.” He jerked a thumb in the direction of the plinth.

Adams, a tall, fat policeman, who kept patting himself on the stomach while he talked, had seen nothing of Walter Brooklyn, whose photograph Ellery showed him. “Lord bless you, if I was to notice everybody I should have a job on,” was his comment, clearly showing his view of the hopelessness of their search. Discouraged, they left him, and went to the station with the sergeant.

Here, the same fate befell them. Neither of the two constables had noticed Walter Brooklyn; and both of them seemed to think the quest quite hopeless. Ellery did not give the name of the man he was looking for, lest the police, intent on building up their own case, might refuse him information. Only an unrecognisable snapshot had appeared in the Press.

“Well, sir,” said the sergeant. “I’ve done my best for you, and I’m sorry it’s no use. But it’s what I told you to expect.” Ellery distributed suitable rewards in the appropriately furtive manner, and prepared to take his leave. But Joan stopped him.

“I have an idea,” she said. “It may come to nothing; but it’s worth trying.” Then she turned to Mulligan, a short, humorous, and very obviously Irish constable.

“Tell me, is there any tramp, or person of that sort, who is often to be found at night in Trafalgar Square? I mean some one you’re always having to move on.”

“Lord, miss, there’s a dozen or so. Move ’em on night after night; but they come back just the same.”

“Well, I want you to find me a man like that—one who’s always hanging about the Square, and is likely to know others who do the same. Can you find me a man of that sort?”

“Certainly, miss, I can. I see what you’re after, and I should say the chap we call ‘the Spaniard’ is about what you want. He’s a bloke who goes about in a long cloak and a broad-brimmed felt hat—often not much else, I should say, barring the remains of a pair of trousers—he’s pretty nearly always about in the Square, and he’s always talking to any one he can find to listen.”

Ellery broke in. “Can you find him for us now?”