People are being told only to travel by train if necessary on the eve of the latest national strikes by rail workers as Scottish transport minister Jenny Gilruth urges UK government intervention to end the dispute.

A strike planned for Wednesday will mean fewer than a tenth of ScotRail services will be able to run on Wednesday, as staff with Network Rail - which owns the UK's rail tracks, stations and signals – walk out during the first of three planned UK-wide strike days.

Some 40,000 members of the RMT union working at Network Rail and 14 train operators will be involved in the stoppage.

It comes after talks over pay, jobs and terms and conditions failed following the biggest rail strikes in 30 years over three days in June.

Just five routes in the central belt will continue to operate between 7.30am and 6.30pm, Scotland’s nationalised train operator has said, while workers are set to picket stations.

Rail passengers heading to and from London faced major chaos before the strikes had even started - with almost every train in and out of King's Cross cancelled due to major damage to overhead electric wires.

Huge queues built up in the waiting area at King's Cross on Tuesday morning as passengers who were hoping to travel in advance of Wednesday's strike were left stranded and scrambling to find alternative routes north.

The chaos meant there were no direct trains on the East Coast Main Line which links London and Scotland.

LNER passengers can use Avanti West Coast or TransPennine Express instead. And its chief executive David Horne said: "My apologies if your journey with LNER today is affected by this disruption. Unfortunately the disruption is likely to continue for the rest of the day - we are running a limited service north of Peterborough only."

The dispute is over a pay and plans to axe hundreds of critical maintenance jobs.

Strike action will also see disruption the evening before on Tuesday and the morning after on Thursday, due to the closing and reopening of signal boxes at different times across the country.

The first train to be cancelled due to the strike is the 5.30pm Grand Central service from Sunderland to London King's Cross tonight, while all Caledonian Sleeper services between Scotland and the capital tonight are axed.

Network Rail Scotland signallers and maintenance staff, who are in safety-critical roles, will take industrial action on July 27, and August 18 and 20.

The only routes that will run on Wednesday are Edinburgh to Glasgow via Falkirk High, Edinburgh to Bathgate, Glasgow to Hamilton/Larkhall and Glasgow to Lanark all at two trains per hour and Edinburgh to Glasgow via Shotts at one train per hour.

“Unfortunately, Network Rail will be unable to open any other signal boxes to operate passenger services on any other routes on the strike days,” a statement from ScotRail said.

HeraldScotland:

“As there will be very limited services running, please only travel if necessary. If you have to travel, you should expect disruption and plan ahead.”

Meanwhile Ms Gilruth transport minister has written to her UK government counterpart Grant Shapps calling for interventionto try to end the dispute between the RMT and Network Rail.

She told him: “I once again urge you to instruct Network Rail to engage in constructive negotiations with the trade unions to reach a resolution.”

She added: “Resolution for staff and passengers is possible, but it will require both political willing and focus.”

However with the Tories currently going through a leadership contest to find a successor to Boris Johnson, Ms Gilruth claimed that “the UK Government continues to appear to be distracted rather than focusing on resolving this dispute as quickly as possible for the benefit of rail users, staff and taxpayers”.

She spoke out as David Simpson, the service delivery director at ScotRail, said that industrial action meant only “around 190” services could run on Wednesday.

The rail operator had only just returned to operating a full timetable last week, a move which meant the number of services had increased to around 2,100 a day.

However the strike action by the RMT, which is taking place as part of a dispute over pay and staff cuts, means that on Wednesday ScotRail will run no trains at all after 6.30pm.

Mr Simpson said it was “frustrating” the strike was affecting services so soon after ScotRail had ended its temporary timetable – which had been in place because of a separate pay dispute with drivers, which has now been resolved.

Only a “very small proportion” of services would be able to run, he stated, with only approximately 9% able to go ahead.

He added this was “very frustrating given how well things have been running since we were able to get back to normal”.

Mr Simpson explained that while the dispute was a national one between Network Rail and the RMT, the action would see signallers go out on strike “They are critical to operating the trains, which is why we have to reduce the service to just a handful of routes tomorrow.”

The National Union of Rail, Maritime and Transport Workers (RMT) in Scotland has confirmed pickets for Wednesday at Glasgow Central, Edinburgh Waverley and Aberdeen.

Network Rail workers plan to protest outside the organisation’s head office on St Vincent Street in Glasgow on Wednesday afternoon as well as outside depots in Irvine, Carstairs, Salkeld Street and Dundee.

HeraldScotland:

The strike action will affect Network Rail operations and 14 train companies across Britain – including some cross-border operators on – causing significant disruption for customers.

Network Rail said only 20% of services will run and some places will have no trains at all on Wednesday.

In a bid to minimise disruption, Network Rail has published a special timetable for Wednesday, with trains set to start later and finish earlier than usual, between 07:00 and 18:30 BST.

On Wednesday, the last trains from London will leave for Edinburgh at 14:00, for Birmingham at 15:43 and Manchester at 15:40.

Mr Simpson added: “Tomorrow there will be a service on just five routes across the central belt, and then there will be a later start up to services on Thursday, because of the opening times of the signal boxes.”

While Network Rail are able to use staff not taking part in the strike to man some of the signal boxes, he said there was a “finite number of those individuals available”, with services focused on lines between Edinburgh and Glasgow.

Mr Simpson explained: “Away from the central belt it’s a much more labour intensive activity to staff these locations and that is why we have had to focus services on these routes.”

A similar level of service was provided during the three days of rail strikes in June, with the same service model also likely to be used if further action planned for August 18 and 20 goes ahead.

The drastic cuts come a matter of days after ScotRail began operating a normal timetable after nearly two months of emergency cuts due to a train drivers pay dispute that has since been resolved.

Mr Simpson said: “We do know that talks are continuing to take place between the RMT and Network Rail, mostly we all hope to see a solution to those for the good of the industry.

“If they are not resolved we can expect a very similar service on those two dates.”

RMT general secretary Mick Lynch said the union would continue to try to reach a deal with Network Rail ahead of Wednesday.

"If we could get a breakthrough then we wouldn't have to take strike action but there's a big gap between the parties at the moment," he said.

"So I'm not going to raise false hopes but we are constantly in dialogue with all of the elements of the industry."

The Prime Minister's official spokesman said: "We are concerned about the impact this will have on the public going about their everyday lives.

"And we will continue to call on the RMT to call off the strikes, it is in their gift to prevent this disruption."

Liam Sumpter, Network Rail Scotland route director, said: “We understand the disruption this strike will cause and apologise to passengers for the impact on their journeys.

“Our industry has been deeply affected by the pandemic, with passenger numbers still at only 75% of pre-covid levels. We must modernise to put our railway on a sound financial footing for the future and reduce the burden on taxpayers.

“We are working hard to run as many trains as possible on strike days for our passengers and freight customers to keep as many people moving as we possibly can.”

The Department for Transport said it was "now clearer than ever" that the RMT has "no interest in engaging in constructive discussions and is hell-bent on creating further misery for passengers across the UK".

"This action is a cynically timed attempt to derail the start of the Commonwealth Games, one of the first major events the country has been able to look forward to since the pandemic," a statement said.

"We continue to encourage RMT to do the right thing by their members and passengers alike and call off the strikes."