Further strike action will hit South Western Railway (SWR) this week as clashes with the Rail, Maritime and Transport (RMT) union show no signs of abating.
The RMT has instructed members not to carry out their duties from the morning of Thursday 21 June to midnight on Saturday 23 June.
The three-day strike has been called owing to the dispute over the role of train guards.
SWR runs commuter services from the UK's busiest station – Waterloo. Later this year, an £800m upgrade will be completed to bolster capacity at the station by 30 per cent at peak times, with the reopening of the former Waterloo International Terminal.
A SWR spokesperson said it would do "everything we can" to minimise disruption to passengers.
Greater Anglia is also facing strike action from the RMT over the role on the guard, which will affect services on Saturday 23 June.
Managing director Jamie Burles has said Greater Anglia plans to run a full service using its contingency conductors should the strikes go ahead.