I'm surprised no-one has pointed out that a major unnerved traffic flow is from EDI/GLA to LCY. There used to be several red-eye flights south by both flybe and BACF, but the latter have closed their Scottish base; tomorrow the first flight southbound from Edinburgh will get you to the City about lunchtime. I'm sure that the market will never recover to the same size, but I would have thought there was enough to make the route viable.
Admittedly when Crossrail finally opens the journey from LHR will be much quicker than now but still..