I’d like to try to understand the flight crew’s decision path.
1. After taking off from LAX, the engine is shut down. The professional consensus is that the flight crew were correct in deciding to proceed (that’s good enough for me).
2. Having so decided, at the same time they chose to return to LHR rather than go to an airport such as BOS (which presumably would have had fewer disadvantages than a return to LAX).
3. Presumably, they made this decision calculating that they would be very unlikely to have to divert to MAN and require a PAN.
4. At some point (only a few hours into the flight according to my great circle mapper), they made a final decision to cross the Atlantic.
5. Similarly, they decided on the same basis not to divert to KEF or PIK.
6. Can I conclude that reasonably non-forecastable event(s) occurred fairly late in the flight?
Feel free to flame this SLF.