Rail bosses are warning passengers not to travel in the coming week unless they have to.
Services are expected to be limited all week and subject to delays, disruption and cancellations.
And on Thursday (5 January) no trains at all are expected to run because members of ASLEF, the drivers’ union, are due to strike.
The RMT has called its members out on strike tomorrow (Tuesday 3 January), Wednesday, Friday and Saturday.
Govia Thameslink Railway (GTR) – operator of Southern, Thameslink and Gatwick Express services – said: “Regrettably, services in the first week of January will be extremely limited with no trains at all on Thursday 5 January.
“This is due to nationwide industrial action by members of the RMT and ASLEF unions.
“Many routes will be closed entirely south of London. Services will start later each day and finish much earlier than normal – from 7.30am to 4.30pm/6.30pm.
“School children in particular should plan ahead and check online at nationalrail.co.uk.
“Gatwick Express will not run but Gatwick will be served by eight trains an hour in each direction by Southern and Thameslink.
“Services will resume after the previous day’s strikes at around 7.30am.”
GTR chief operating officer Angie Doll said: “We’re really sorry for the disruption this ongoing RMT action will cause our customers over the entire festive period, until Sunday 8 January.
“Regrettably, due to industrial action, our train services will be extremely limited in the first week of January with no trains at all on Thursday 5 January.
“Please plan ahead and, if services are running, travel only if absolutely necessary.
“Services could also be subject to last-minute change on other days beforehand.
“Vital engineering work is also closing much of the route north of London to Peterborough on Saturday 7 January and Sunday 8 January. Alternative travel advice is available online at nationalrail.co.uk.”
Daniel Mann, director of industry operations at the Rail Delivery Group, said: “No one wants to see these strikes go ahead and we can only apologise to passengers and to the many businesses who will be hit by this unnecessary and damaging disruption.
It makes a change from the usual Govia excuse of signal failure.
The irony now being that workers have lost more in income because of the strike action that the raise they actually wanted. The whole event is so self destructive.