Split Infinity was inspired by the 'make your
own adventure' books of the mid 1980s and came out of a desire
to make the AFT a more interactive experience with readers
choosing the fate of the main characters. However as the DWM
review of the AFT rightly pointed out, some of the readers'
options weren't exactly earth shattering.
At the time this was the longest single episode
for the AFT. The twists and turns and alternative routes took a
lot of working out so even if it had been successful, the
experiment was unlikely to ever be repeated. The scenes on the
planet Calameth were filmed in a real quarry (near Audley End)
in honour of the TV show's use of such locations.
While some people responded favourably to the 'make
your own' parts of Split Infinity it appeared that most
readers preferred the site to be a more passive affair
so the 'cheat' button was created enabling the story to
be read linearly. This option sidestepped Leela's part
in the adventure. The cover for the story was based on
the covers for the 1980s 'make your own adventure' books
which had featured the sixth Doctor.
In the subsequent years, Split Infinity became
regarded as a slightly substandard AFT story. An attempt to
rectify this was made in early 2005 during some housekeeping on
the site in the run up to the beginning of the new series. Split
Infinity was re-edited into three episodes discarding the
various dead ends and alternate endings (reprinted here). It
also received a shiny new cover.
The inclusion of Leela and K-9 clearly place the
story during season 15 (between The Invisible Enemy and
The Invasion of Time) It was arbitrarily placed just
before The Invasion of Time but nothing in the story
states this specifically.
In terms of the AFT continuity, this story marks the
introduction of Thadius Torchwood beginning the AFT
first arc: something that had been planned since the
beginning. Torchwood appears in the background of the
previous two adventures (Harvest of Death and
War of the Cybermen) and goes on to appear in The
Diary (a spin off adventure), The Changing of
Bracchis, The Dalek Invasion of Time and
Crystal Palace before beginning his own series
(sadly cut short after one episode) It is worth noting
that Torchwood was created in 2001 long before the new
Dr Who series and it's anagramically named spinoff.