Colin Rosenstiel wrote:

It attempts to abstract from Cambridge-Birmingham, despite Central
running through trains that take less time. Try looking up
Cambridge-Birmingham on the NRE web site some time.

A quick query showed a few routes. None of them included the X5.
Putting in via Milton Keynes Central gave a load more - again not
including the X5.

The journey planner shows the quickest connection at any given time,
AIUI, so long as it is a ticketable permitted route (plus a few
exceptions to this).

Are you sure there wasn't engineering work on the day you tried the
query?

Neil