Yes thank you, you are of course correct - I have actually raced Fireballs once on King George V and should have remembered. Again almost always a weekend pursuit of course.
You should never put others on the ground at risk. It begs the question whether ditching on a resevoir or in the Thames is unreasonably putting others at risk. Landing on occupied playing fields clearly is and must be avoided at all cost, and nor should the pilot put himself in a situation where he has no alternative.
There are numerous approaches and departures I can think of where an engine failure at a critical time would almost inevitably leave the aircraft and occupants in the houses unless they were very lucky, and although I know some would argue this is not so, the evidence would not seem to support the case.