I ask simply because I don't understand why they took the risk of flying 20 miles over central London on 1/2 an engine when they had a great runway a few minutes away
What "risk" did they take in pilot decision making terms? What track miles from their position when they took their decision was STN22 v LHR 27R? Were track miles / time to land uppermost in their mind? What additional time would it take to brief an approach to somewhere unfamiliar than somewhere you've landed at 20x a month for the last X years?
You clearly know the answers to those, so will await with interest. I haven't a clue, but suspect in the same circs it is 95% likely I would have used LHR 27R.