“Perhaps the reason why the Phillimore Terrace robbery was never brought home to its perpetrators is because there was no woman in any way connected with it, and I am quite sure, on the other hand, that the reason why the thief at the English Provident Bank is still unpunished is because a clever woman has escaped the eyes of our police force.”

He had spoken at great length and very dictatorially.  Miss Polly Burton did not venture to contradict him, knowing by now that whenever he was irritable he was invariably rude, and she then had the worst of it.

“When I am old,” he resumed, “and have nothing more to do, I think I shall take professionally to the police force; they have much to learn.”

Could anything be more ludicrous than the self-satisfaction, the abnormal conceit of this remark, made by that shrivelled piece of mankind, in a nervous, hesitating tone of voice?  Polly made no comment, but drew from her pocket a beautiful piece of string, and knowing his custom of knotting such an article while unravelling his mysteries, she handed it across the table to him.  She positively thought that he blushed.

“As an adjunct to thought,” she said, moved by a conciliatory spirit.

He looked at the invaluable toy which the young girl had tantalisingly placed close to his hand:  then he forced himself to look all round the coffee-room:  at Polly, at the waitresses, at the piles of pallid buns upon the counter.  But, involuntarily, his mild blue eyes wandered back lovingly to the long piece of string, on which his playful imagination no doubt already saw a series of knots which would be equally tantalising to tie and to untie.

“Tell me about the theft at the English Provident Bank,” suggested Polly condescendingly.

He looked at her, as if she had proposed some mysterious complicity in an unheard-of crime.  Finally his lean fingers sought the end of the piece of string, and drew it towards him.  His face brightened up in a moment.

“There was an element of tragedy in that particular robbery,” he began, after a few moments of beatified knotting, “altogether different to that connected with most crimes; a tragedy which, as far as I am concerned, would seal my lips for ever, and forbid them to utter a word, which might lead the police on the right track.”

“Your lips,” suggested Polly sarcastically, “are, as far as I can see, usually sealed before our long-suffering, incompetent police and—­”

“And you should be the last to grumble at this,” he quietly interrupted, “for you have spent some very pleasant half-hours already, listening to what you have termed my ‘cock-and-bull’ stories.  You know the English Provident Bank, of course, in Oxford Street; there were plenty of sketches of it at the time in the illustrated papers.  Here is a photo of the outside.  I took it myself some time ago, and only wish I had been cheeky or lucky enough to get a snap-shot of the interior.  But you see that the office has a separate entrance from the rest of the house, which was, and still is, as is usual in such cases, inhabited by the manager and his family.