The logic was that the thought of the landing fee might cause pilots to press on when they should divert.
I wonder what genuine work was done to prove this, or whether it was just a conjecture? Like others I find the idea of choosing to kill oneself to save a few quid, which is hardly going to make a material difference to the overall cost of the trip, utterly bizarre.
OK, so if one were faced with paying several hundred pounds at Heathrow or Gatwick or Stansted one might appreciate a free landing in an emergency ... but Heathrow and Gatwick aren't on the list, and last time I ran into worse-than-forecast weather on the edge of Stansted's zone the nice man at Luton Radar was offering me a wide choice of nearer runways. On balance I think I'd still prefer to pay the several hundred and stay alive.
Personally If I had a genuine Wx diversion I would be so grateful to be safely down in one piece that I would't dream of quibbling if asked to pay.
Indeed. I think I probably wouldn't even accept the free landing if offered!