Back in the 80s of course there were no trains from Guildford platform 1 to anywhere other than the Cobham route. But "Takt" style good connections, half-hourly, at Effingham Junction applied for passengers who wished to travel that way. Every Cobham line service was announced at Guildford as "change at Effingham Junction for Epsom".
In 1982/3 for example (the timetable is available on Timetable World, and I have a CWN for this year), the Effingham Junction terminator alternated between Waterloo (SWD service) and Victoria (Central Division service), so places like Sutton would have had an hourly service to Guildford by good connection.
Looks like Effingham had very extensive sidings in those days too (CWN mentions Roads No.2 to No.7; but no No.1?). Not sure if these still exist, I've only traversed the Cobham line in daylight once, and that was in 1988.
That is really good news. Can never have enough trains stopping their. I would say that though.
Presumably allowed by the non-existence of the 1818, so there's a spare path behind it.
More generally, why have the regular off-peak fast ('81') services on the Portsmouth Direct
never called at Clapham, from what I gather? Right back to 1985 when Clapham calls started appearing on mainline SWD services.