No such thing as an assured landing - had heathrow close with both runways blocked - two in incidents within half an hour....daytime in good weather. Burning alternate fuel at your destination always seemed a foolish gamble.
You're piling one inference atop another for planing purposes. Are you scared?
"In daytime in good weather" as you say. . . during your emergency, (declaring MAYDAY), how much fuel would you need to fly
23 nautical miles for a straight-in visual to LGW or LTN...?