MANFOD,
If I remember correctly, arrival spacing of between 10 and 15 miles are often common during LVPs. Later on this month, an 18 week duration H24 closure of TWY Alpha between A2 and A3, is, I believe, is due to come into operation. Associated with this is the closure of link AF and RET AE, for the period. This will mean the SW and of TWY A will become an isolated 'turning-loop', which will necessitate 'backtracking' by a/c which fail to vacate at Link 'B'/RET BD.
When 05L is in use, backtracking will also be required for those a/c unable to depart from Link B, (TORA 2036m).
The fog-forecasting became less accurate decades ago, with the closure of the EGCC regional met office, and it's relocation, initially to Daw Bank, and subsequently to Exeter.
Also, the met observations are now made by ATC staff, using the SAMOS system. The dedicated Met Office observers moved out about 10-15 years ago, if I remember correctly?