I loved the idea of the Olverung, and the story was certainly well-written in terms of things like characterization, flow, and so on, but oh mercy me, that man was the worst "master thief" I have ever seen. He left two clear witnesses who can finger him - his old mentor who knows he purchased the Grey Gentlemen (and even used that same name during his show!) and the footman who personally led the rogue magician directly to the king's quarters with knowledge that said magician was specifically interested in the Olverung. Plus he thinks Lord Atherton might have recognized him or realized who he was.
Now, the fooferah at the end, yeah, unfortunate, bad luck, somewhat unavoidable, and that left lots more witnesses, though most wouldn't have gotten a clear look at his face. But his plan was terrible on the face of it. What if they'd turned him away at the gates? He didn't have any tokens from the lady or any sign of being in her employ. Why wear a mask during meetings at night in a graveyard but NOT during a magic show, when one could presumably get away with it fairly easily? For that matter, why do a magic show at all? He could have just bribed the footman from the get-go. You want to avoid visibility and drawing attention to yourself when pulling a heist. I mean, it's great to have a magic show as a distraction, but then you need a minion to pull the actual theft. Plus, leaving a pigeon behind is going to kind of clue everyone in on who pulled the crime if you just used those pigeons in a magic show. Oi.
And he maintains a public identity with a very large house. That's only a good idea if you're stealing money from your own corporation. If you're a second story man, you need to either live in quiet opulence or have a good reason why you're wealthy. "Poor orphan" isn't a great background for that.
Perhaps this is a sore point of mine. I've read several fantasy novels with a "master thief" protagonist who doesn't take even basic common sense precautions when pulling heists and whose "brilliant plans" are full of terrible holes. (I remember one rather vividly, save for the actual title, in which the super-genius hero's Big Secret Plan involved just crashing a party, snatching the valuable MacGuffin, and running.) I think it's just a weakness of the genre.
Let me see if I can think of what I'd call a good example, just so this whole post isn't whining. Hm. Juliet E. McKenna's series starts with "The Thief's Gamble" and, while it's not without flaws, does have a thief protagonist who approaches the job with the right mindset. And it's been a while, but I don't remember facepalming at any of the plans in Martha Wells' "Death of the Necromancer," which even has a super-master-thief (complete with Sherlock Holmes analogue chasing him) as a protagonist instead of just a standard cat burglar.
So yeah. Loved the idea of the bird and the general story arc, but frustrated by the bad-idea-on-the-face-of-it plan from a supposed career criminal. That about sums up my reaction.