I was relaxed about the Citation flying under my flght, ( I was a passenger I hasten to add ) as I know LCY departures are restricted to 3000 ft in the first instance and LHR arrivals aren't supposed to be below 4000 ft.
I have seen this maneuvour many times as I was local to the area, my concern is that this is the second reported time in recent years that a large airliner has been involved in a loss of seperation over a densely populated part of London.
It ought to be possible to route Heathrow arrivals far enough East or West of LCY departures but maximising the use of the airspace means that some of them are descending right on top of LCY departures climbing towards them. As a layman it's far from ideal IMHO, if the professional says it's safe, I'm just asking why given the Air Canada incident, it seems to have happened again in the sane place.
Not a journo, just an ex local.