"Matt Wheeler" gurgled happily, sounding
much like they were saying:

Will wait for someone to confirm, but at a guess, it may be an
Amersham/Chesham to Watford service that weekend. This would seem
likely, given an earlier closure on 27/28 June is listed as Harrow on
the Hill to Amersham, Chesham & Watford.

That was my first thought, but for the "/Rickmansworth". That'd imply
that there's nothing south of Ricky on the Amersham branch, to my mind.

shrug