“Of course—as many moments as you like.” Prince Soudaroff’s godson knew something of his methods of working. “Am I to do anything?”

“Only watch me, and when I succeed in approaching Texelius, distract the attention of the detectives for a second or so.”

“Very well, Prince.” The secretary was not without practice in work of the kind, so that when Dr Texelius had finished haggling with his porter over his charge, he found himself confronted by a dapper gentleman, exquisitely dressed, whose grey moustache was waxed into points of needle-like sharpness.

“I have the honour of addressing the Herr Professor Texelius?” said the stranger hurriedly in German, laying one finger on his lips.

“I am that most shamefully ill-used man,” snorted Dr Texelius.

“You would like to expose the Mortimer?”

The philosopher’s eyes sparkled. “Only give me the chance!”

The other drew out a sealed envelope, and slipped it into his hand. “That will provide you with the means of doing so. Hide it at once. I am Soudaroff.”

With a dexterity which a professional conjurer might have envied, Dr Texelius made the packet vanish up his sleeve. “It shall be done,” he said.

“When does your paper appear?”