Waiting for TBS, like everyone else.
Actually, we've been using time based separation at Gatwick (and presumably many other airports) for at least 20 years, it's just that we express it as a distance because that's what the approach guys and girls see on a radar screen. Hence departure gaps vary between 7nm (slight tailwind), 6nm (calm), 5nm (reasonable headwind), or even 4nm (stonking headwind) with .5nm variations to tweak the gap to achieve the same time between landers...so time based separation is actually nothing new though I'm sure an expert somewhere will claim to have invented this magnificent innovation though....
