Saturday 13th August
I've received an email from TfL today advising "On Saturday 13 August, a rail strike is planned by ASLEF union members working for nine train operators across the country, which will mean minimal or no service on many routes into and out of London. This includes the London Overground network, where no service is expected on either London Overground or Night Overground."

Last time London Overground ASLEF members were on strike Southern didn't operate the stopping service to London Bridge/East Croydon as they claimed the stations on the route which are managed by London Overground were closed. At the moment the route is still showing as operating on rail journey planners but this may well change between now and Saturday!