JammedStab: I think you are referring to the BOAC B707 which dropped an engine into the Staines reservoir and made a successful landing back at LHR on the then runway 05. Showing my age here! The 707 in those days had separate LP and HP fuel valves, the former on the engineer's panel - and yes, that item was missed but resulted in valve position lights being retrofitted to the aircraft to obviate a recurrence. More modern types combine the two valves functions.