There are a couple of common routes through the "London Zone". There is Burnham "corridor" to the west of Heathrow and the "corridor" over London City and up the valley. The Burnham corridor as others have said is always not above 1500 feet or 1000 feet, London City is usually not above 2500 feet I seem to remember.
I think this is a very interesting topic because of the land clear implications and a recent comment in Gasil this edition which caught my eye. Gasil made the point that the Courts do not consider the London City route provides adequate land clear opportunity for a SE.
I would be interested in people’s views on this aspect from a number of viewpoints. Firstly, I gather single engine approval for commercial operation including in IMC is about to be granted, albeit I guess for turbo props. Should they suffer an engine failure and "breaking through" the overcast at say 1000 feet perhaps over a city how well will they cope or will their commanders be sufficiently situationally aware to vector themselves to a non built up area? Secondly, using for example the Burnham corridor at 1000 feet or following many departures from "City airports" realistically would we guarantee to land clear? (And I appreciate the rule exemption on arrivals and departures).
In summary is the comment in Gasil yet another attempt to curtail the airspace in which we are free to operate or should we be avoiding these low level routes through built up zones because of the risks to ourselves and others which the Courts are rightly enforcing?