Nice little anecdote illustrating how the craft of the historian is similar to that of a detective. Here's Richard Cobb playing Sherlock Holmes (more credibly than Benedict Cumberbatch was able to given the plot in the last episode: like antiques from china, it was very far-fetched):
At 4'o'clock one morning in a tabac in the rue du Four, I met a very drunken couple. One was a civilian pilot, who was to fly the next morning, and who had already been threatened with removal of his licence after a drunken landing. The other was a very well-dressed, rubicund man, with neatly brushed black hair, a hat with a dark band, well-kept hands, and a diamond pin in his tie. He looked professional and was at first reticent. But by 5 o'clock he was anxious to speak of himself, and gave me a number of hints. 'I am a Belgian; I come to Paris for the summer; I only work here in July, August, and early September; I only work in the XVIe and the XVIIe. My work in involves me with Post Offices, female servants, and chauffeurs.' It did not seem very difficult; I told him he was a professional housebreaker. He was delighted, opened a handsome pigskin bag, displaying some hundred instruments on runners. He was a man who enjoyed his work, but he also like talking about it, and needed an audience.
They seem to have had a better class of burglar in the old days (this was probably in the '50s) - just look at the Pink Panther films for corroboration. And housebreaking has so much more class than burglary, don't you think?
What took the practice so downmarket? Drugs?