SJCWHUK ) gurgled happily, sounding much like
they were saying :

But be warned, when 'maximum fare' comes in you will be charged
either £3.60/£5.50 (zone 1-6/zone A-D).

How will they know if you had an uncompleted journey to zones A-D?

Because if your uncompleted journey started at Amersham but they don't
know where you exited it will be £5.50.

But if the uncompleted journey *finished* in zones A-D...?