The UK's claims to have a world exclusive on just how tall the world's tallest building will be. Emaar is keeping mum, but apparently a structural engineer working on the building has spilled the beans: 890.7 metres. This magical figure was arrived at by adding the height of the Empire State Building (448.7 metres) to the Sears Tower (442 metres). Or at least, that's what the reporter guessed and then was cryptically told that "you wouldn't be far wrong if you put those two together", leaving the door open for this to all be just another wrong guess. Thanks to for tipping us off.