Aviation Herald finally noticed this incident - such as it has for info, roughly corresponds to wiggy's statement.
Some kind of bureaucratic flight-plan filing/amending issue that resulted in enough in-flight delay entering Russian airspace to run into either fuel or crew-time limits.
Incident: British Airways B773 at London on Jul 7th 2016, 12 hours flight covers 0nm
Since they were able to U-turn, but not continue, one wonders if there was a problem with forecast winds as well.
So now I tell you how we fly to America. The first time we started we got-a half way there when we run out a gasoline, and we gotta go back.... - Chico Marx in A Night at the Opera