QUOTE Yet interestingly not a single post that answers the question of what actually happened to the engine in question.
The Aviation Herald
www.avherald.com usually a very reliable source say that
"the crew detected an oil leak in engine #1 (Trent 970, outboard left hand) and decided to shut the engine down".
Nothing is said about how it was detected, i.e. oil observed on engine cowling or decrease in measured quantity.