Was it the Queen purring? Or was that just the sound of the dial tone after she hung up on David Cameron? Or perhaps he was mistaken and she was snoring? Either way the monarch's supposed expression of smug, Goldfinger-like satisfaction after learning the results of the Scottish referendum caused poor old gammon face to have to make an embarrassing and spluttering apology - sort of like an animal having its nose rubbed in the mess it's made.
But it was too late. The internet doesn't need much of an excuse to make with the cute cat pics - its second most favourite thing, after porn. Cue a million single women dusting off a million prom night tiaras, placing them on their cat for the evening and captioning the resultant pictures with things like "purr majesty will see you now."
In fairness to Cameron, there are worse animals he could have connected Lizzie with. It wasn't like he said she made a fool of herself by snorting with delight, Fergie style. He never claimed she did a full moggy impersonation, like George Galloway. And any politician-queen relationship should have a small element of sexual tension - there's something about 'The PM and the purring Queen' that sounds like it could be a 50 Shades-style bestseller.
And it's true, cats are fairly regal animals, but it's just so hard to imagine HRH making such a noise. Short, sharp barks, yes. Hissing, perhaps. But purring? it would frighten the Corgis.