Mark 1, correct up to a point. London is a congested area for FW as was proved some years ago at the trial of someone who tried it on and claimed he could pull off a forced landing safely in Hyde Park. Oh NO! said Mr CAA, thats land used for public recreation and so not allowable, its a Congested area!
He should have known better as it was not an area of 1000ft radius/diameter (chose which definition you please as the CAA seem to do, but steadfastly refuse to define) less than 50% "Congested", though if Hyde Park is "Congested" compared to the rest of London then my c*ck is a kipper.
Even so single engined helicopters can operate over the Thames from Greenwich to Kew, as well as over Richmond Park, Twickenham and Hampton Courtand other urban areas all of which are as "Congested" as Hyde Park with official sanction.
Figure that out if you can.