As I understand it, Southern's Watford - Brighton services (via
Olympia and Clapham Junction) usual calling pattern southbound is

Harrow & Wealdstone, Wembley Central (sometimes), Olympia, Clapham
Junction, East Croydon, Gatwick Airport, Three Bridges, Haywards Heath
and Brighton

Idly browsing today, however, I found that the 1727 ex Watford - and
apparently *only* this service, all day! - additionally calls at
Streatham Common and Selhurst. Not at any of the other suburban
stations en route from Clapham Junction to East Croydon, mind - just
those two. Just that service.

Why could this be?


--
Larry Lard
Replies to group please.