Might I ask, respectfully, as to why any 747's would want to land/be diverted to LTN when STN is just close by
First of all, probably when diverting the weather at STN (and elsewhere) being below limits, don't forget these where older 747s (100-200-300) which were CAT II or at best CAT IIIa. Secondly some needed to be at LTN for commercial reasons.