Now I've heard of a drop scone, but until yesterday I'd never heard of dropping your Victoria sandwich in the tin as soon as it's come out of the oven. This apparently stops the middle from sinking as it breaks the walls of the bubbles and allows the air to get back in. The outer edge of the cake gets to a hotter temperature and therefore is cooked more than the centre. I have certainly dropped cakes in my time....on the floor. Now I get to drop them intentionally on the work surface!
So now you know- there was a fuller explanation on Nigel Slater's Icing on the Cake programme.