This is more of a personal inconvenience than a real problem, but why
does the Metropolitan Line feel the need to schedule northbound trains
to terminate at Wembley Park and reverse into Neasden through the
diveunder? In theory, this shouldn't be too much of a problem, if
there is enough time to allow the next service to pass through Wembley
Park before reversing, but the margin of error can easily vanish. As
taking the train into the diveunder blocks all Met trains coming
north, this can mean a delay of two to three minutes at the best of
times. A hitch in detraining or a signalling problem can cause all
trains coming up from Finchley Road to be seriously delayed.

The real problem is that the diveunder does not allow for a northbound
Met to pass into Wembley Park while the train is reversing into depot.
Trains, however, could be halted further up the line. More southbound
trains from Amersham or Watford could terminate at Harrow-on-the-Hill
or Wembley Park and run straight into Neasden on the fast lines
without impeding any other traffic. A less satisfactory solution would
be reversing at Harrow (if the siding is free) or other northbound
stations. Scheduled reversals into the diveunder during passenger
hours should be kept to an absolute minimum.