Ron & Edna,
The engine being shut down at the point you suggest makes a lot of sense, as far as diverting into FRA versus continuing to LHR, especially if LHR's weather was looking dodgy. As I said above, the fuel burn doesn't really go up with one engine shut down but, obviously, you end up cruising at a slower speed, the flight time is longer and, overall, you end up using a bit more fuel due to being up there longer. Couple that with a poor forecast and it sounds like the crew made excatly the right decision (something I never questioned for one moment).
Depending on the individual companies, an engine shutdown on a Jumbo can make almost no difference whatsoever to the actual operation of the beast. The aircraft is still certified for Cat IIIB operations with 3 engines (and autolands just as well with 3 as with 4) and, again depending on company rules, if you calculate you have enough fuel you can continue the flight even if it's only just started i.e. lose one engine on takeoff. It's a great machine
