We already know:
- It was part of Southern Region prior to sectorisation
- It was not covered by the Railways Act 1921
- It was open at least on the 1st of January 1948, and is open now
- It's south of the Thames (it's not north of the Thames, but the only station that straddles the Thames to my knowledge is Blackfriars and that's inside the M25)
- It's outside the M25 (this precludes all parts of the London Underground + the East London Railway)
- It HAS direct services to London (I take from the way that question was worded that direct services continue to this day)
- It's therefore in Surrey, Berkshire or Kent (county bordering Greater London, station south of the Thames).
I'm assuming that by "direct services into London" it has direct trains to a London Terminus (with the restrictions this is precisely the set of London Bridge, London Cannon Street, London Charing Cross, London Waterloo, London Victoria, London Blackfriars and London St Pancras International - High Speed Section).
To my knowledge, all direct trains into these termini are the preserve of Thameslink, South West Trains, Southern or Southeastern.
These are all the stations in Surrey, Kent or Berkshire (though none in Berkshire) which opened between 1923 and 1948 and are outside the M25. So my next question is, is it one of these six stations?
Longcross (Waterloo to Reading Line, 1942, irregular peak hours service to Waterloo)
Aylesham (Dover Branch/Chatham Main Line, 1928, Victoria)
Chelsfield & Swalecliffe (Ramsgate Branch/Chatham Main Line, 1930, Victoria)
Dumpton Park (Ramsgate Branch/Chatham Main Line, 1926, Victoria)
Kemsley (Sheerness-on-Sea Line, 1927, a couple of trains to Victoria)
Ramsgate (Loads of lines, 1926, Charing Cross/Victoria/St Pancras International)
All London buses: 23 hours 25 minutes (with Adham, David, Josh and Tangy)
Holds some alternative challenge records. Not sure which ones.
20½ Random 15 challenges: 01:58:48 best
That guy who runs those Twitter polls about tube stations and London Boroughs.