South Western Railway workers are set to strike for most of December, it has been announced.
Members of the Rail, Maritime and Transport Union (RMT) will walkout for 27 days throughout December.
The move threatens to cause travel misery or thousands of people over Christmas, but the union said it had been "left with no choice".
RMT has been in a long-running dispute with SWR over guards' future roles amid concerns their jobs could be eliminated as driver-operated new trains come into service.
Here's everything you need to know about the RMT December strike.
What dates will workers strike?
The walkout will take place for 27 days between December 2 and New Year's Day.
According to RMT, members will not book on for duty from 00:01 on Monday December 2 until 23:59 on Wednesday December 11.
They will also not book on from 00:01 on Friday December 13 until 23:59 on Tuesday December 24 and from 00:01 on Friday December 27 until 23:59 on January 1.
This means that strikes will not take place on Sunday, December 1 and Thursday, December 12.
Where do SWR trains run and how will it affect me?
South Western Railway trains cover a large swathe of area in southern England in Surrey, Hampshire and Dorset.
Regional services also run in Devon, Somerset, Berkshire and Wiltshire.
The company's main terminus is at Waterloo, while other London stations services run through include Clapham Junction, Vauxhall, Wimbledon, Kingston, Surbiton, Brentford, Twickenham, Wandsworth and Putney.
Other major destinations along the route include Weymouth, Basingstoke, Southampton, Winchester, Bournemouth, Portsmouth, Woking, Reading, Sailsbury, Guilford, Exeter, Yeovil, Reading and the Isle of Wight.
Why are workers striking?
It's part of a long-running dispute between the union and SWR over guards on trains.
The union wants guarantees over the guards' future roles amid concerns their jobs could be eliminated as driver-operated new trains come into service.
RMT general secretary Mike Cash said: "At the last meeting we held with SWR, principles in agreements were made in good faith with the company's negotiating team and we now feel hugely let down again.
"As long as the company continues to refuse to give assurances on the future operational role of the guard, we will remain in dispute.
"I want to congratulate our members on their continued resolve in their fight for safety and the role of the guard on SWR. It is wholly down to the management side that the core issue of the safety critical competencies and the role of the guard has not been agreed."
What has SWR said?
SWR said it was "extremely disappointed" with the move, saying it "is typical of the lack of concern the RMT continue to have for our customers".
The spokesperson added: "The RMT has always said it wanted us to keep the guard on every train. That is what we have offered as part of a framework agreement if the RMT work with us to agree a method of operation for our new trains which fully utilises the new technology to improve safety, security and accessibility as well as day-to-day performance. Instead the RMT appear purely focussed on keeping control of train doors in a misguided attempt to hold power over the industry.
“Whilst we have shown commitment to the role of the guard by introducing over 80 additional guard roles since the start of our franchise, the RMT do not have the long-term interests of either our customers or our colleagues, including their members, at the heart of their actions.
“We remain committed to finding a solution that will help us build a better railway for everyone. We will do everything we can to keep customers moving during strike action.”
