The original service was started using a batch of 60 319/0 stock delivered by 1988. A second betcha of the class 319 was introduced from 1990, that was configured for the longer journeys from Bedford to Brighton with 1st class seating and Brecknell Willis pantographs. This enabled a fuller service after 1992.
Ah OK thanks. In the 90s I drifted away from the "Central Division" / Connex so wasn't fully aware of goings-on there: basically all I saw were the Victoria-Hove-Southampton and Victoria-Horsham-Portsmouth routes and the Coastway West Portsmouth stoppers.
Thanks also for the other replies.
I did however see the original Thameslink service in 1988 so remember the original pattern of alternate Brighton and Gatwick terminators.
Yes, via Tulse Hill and West Croydon, then as the peak extras through Sutton, Epsom and Bookham.
Before Thameslink, the Sutton loop was covered by a strange service that ran London Victoria - Balham - Mitcham Junction - Sutton - Wimbledon - Tulse Hill - Peckham Rye - London Bridge
I remember this varied by year. In 1985 for example the Wimbledon Loop went Victoria - Norbury - West Croydon - Sutton - Wimbledon - direct route, presumably - Holborn Viaduct.
Alternate services must have waited somewhere though, because the pattern out of Holborn was half-hourly (on the hour and half hour, IIRC) but at Victoria was 20/40 (xx02 and xx42, part of a 20-min interval stopping service via Norbury with the xx22 to Epsom Downs). The timetable made it look as if the ex-Victoria services terminated at West Sutton as there was no "To Holborn Viaduct via Wimbledon" note.
(I remember this as I attempted to memorise the timetable prior to my first visit to Clapham for rail enthusiast purposes on 31/12/85 !)