The 319s carried alphanumeric codes in the second destination display in the 1990s. The system didn't last long. NSE introduced route numbers on new-build stock - eg 321s, 165s, 166s, 465s. Again, the use of these numbers fell away.
Yep they were instigated at the bequest of the then MD ('big-Jim' Collins) I think, though it may have been part of a wider NSE initative that didn't come to nowt in the longer term. I developed them as Resources Manager at the TOC and with only a limited number of characters to display only a 2 digit code it was a bit of a challenge to say the least. It wasn't helped by the seemingly random nature of some (peak) calling patterns in particular, but this was simply because we were so resource driven and much of the time running to keep up with demand that we had to constantly tweek calling patterns to reduce overcrowding or attempt to even out loadings. From memory they were something like this;
Thameslink Alpha-numeric route codes (early 1990s);
Destination (first digit):
B Bedford
G Guildford or West Croydon
H Brighton via Red
Hill
L Luton
M Moorgate
N St Alba
Ns
O Selhurst?
R O
Rpington
S Sevenoaks
T Brigh
Ton via Quarry
U S
Utton
W Gat
Wick Airport or Three Bridges
Calling pattern, mostly north of the river (second digit):
1 All stations (Bedford to Farringdon) and v/v
2
3 All Bedford to St Albans and then via London Bridge and v/v
4
5
6
7 All stations Bedford to St Albans then via Elephant and Castle (though not necessarily calling at E&C!) and v/v
8 Semi-fast (Luton or St Albans then Radlett, Elstree and Mill Hill Broadway) then fast to Kings Cross TL and v/v
9 All stations (Bedford to Farringdon) except Kentish Town and v/v
0 Other please check timetable!
X Express, (Kings Cross TL fast to Luton or Flitwick) and v/v
There was some restance from some colleagues at Train Planning Railtrack (as was) not least as some of the route codes on the headers of the timetable columns could be confused with days of the week, SX, S0, MX, M0, especially in the then GBTT, though as these designations are used mostly by rail staff it was thought that the general public wouldn't be too confused! In the main our own traincrew mostly correctly displayed them, though at times of disruption and on the 'wall of death' they sometimes didn't get correctly changed when changing direction. They were also shown on CIS screens (at least North of the river where we operated the stations) but as this was before the days of automated on-train announcements again it was up to the traincrew to add them to their announcements.
Oh and Big-Jim was known as such due to his stature (well over 6ft!)