text: Thousands of signallers, maintenance staff and station workers are due to walk out for 24 hours from 17:00 BST on Monday in a row over pay and jobs.
  If they do, limited services will run on Scotrail, Gatwick and Heathrow Express lines and Southeastern.
  And there will be no Virgin West Coast mainline services on Monday or Tuesday.
  The operator, Virgin Trains, also warned that the East Coast line would be badly affected.
  Widespread cancellations are also expected to be announced on CrossCountry Trains, Chiltern Railways, Arriva Trains Wales and First Great Western on Monday and Tuesday.
  Rail companies say further disruption and delays are likely on Wednesday, as services return to normal.
  If the strike goes ahead, fans of Middlesbrough and Norwich City football clubs may have trouble travelling to Wembley for the Championship play-off final at 15:00 BST on Monday.
  An outline of how the strike will affect all train companies is expected today, with full details likely on Saturday - but passengers are being advised not to travel unless "absolutely necessary".
  Talks between Network Rail and union bosses at the conciliation service, Acas, are continuing.
  Members of the Rail, Maritime and Transport (RMT) union and the Transport Salaried Staffs Association (TSSA) have rejected a four-year pay deal of a Â£500 increase followed by three years of rises in line with RPI inflation.
  Virgin said if the strike was called off with enough notice, it would hope to run a "near normal" service.
  But Network Rail chief executive Mark Carne has advised travellers not to "bank on" the unions calling it off, although he still believes there is "a settlement to be had".
  He said his team would be available all week and into the weekend if necessary, to reach a deal.
  People who have already booked tickets should check with their train operator on the special measures in place, he added.
  RMT general secretary Mick Cash said his team were also prepared to continue negotiations over the weekend.
  "In the meantime, our picketing arrangements are in place and the response coming back from our members is one of rock-solid support," he added.
  The RMT has been forced into this dispute through "a wholly-unwarranted attack on safety-critical jobs, pay and working conditions" that undermines passenger safety, he added.
  Scottish transport minister Derek Mackay said the strike was "very likely to go ahead" and have a "significant impact" on rails and roads.
  ScotRail Alliance managing director Phil Verster, said the firm was "very disappointed" to have to make so many cancellations but, as it was a UK-wide national strike, "there's very little we can do about it from the Scotland side".
  He told BBC Radio Scotland 470 Network Rail signallers could strike and he has only 23 contingency signallers so "our capability to step in is very, very limited".
  Later, the High Court is due to hear a challenge from Network Rail over flaws in the ballot by the TSSA.
target: More rail companies are cancelling services over the bank holiday weekend, as talks continue to try to avert a planned strike by Network Rail staff.