Time between leaving train and signing off.

Generally nil (typically duties book off on the platform, although some
do have up to 7 minutes at the end).

According to District Dave's website
(http://www.trainweb.org/districtdave...318_duty.html), there's one
duty on the District Line with an hour and six minutes between leaving
the train at Barking EB and booking off at Earl's Court.
(Incidentally, this website's well worth a look at - the story about
him ending up at South Harrow is HILARIOUS!!!)