The British capital's officials were said to be "highly confused", as they had not discussed a reprise of the stunt with the eccentric magician.
Less than 2 hours after Blaine's box appeared in the London sky, however, he seemingly vanished again. Onlookers squealed with delight, thinking it was all part of the trickery. Yet a police helicopter was able to see that the box now only contained a black and white cat.
An hour passed, with authorities unsure of what to do. Then the cat/Blaine leapt through the box's north-facing wall, without breaking it, and landed nimbly on the ground.
Crowds scattered as trained police officers picked up the nonchalant animal.
Blaine's manager Marcie Christ told The 666 O'Clock News: "To be honest with you, this is not a public appearance I had anticipated. David did not discuss this with me at all. It's very strange. All we can do is feed the cat and wait."