Travellers heading to Europe should soon be able to resume their journey after a deal was done to end a strike that halted cross-Channel trains.
Thousands were stranded on Thursday when French workers rejected an end-of-year bonus.
Services affected included Eurostar, which runs passenger services from London St Pancras, and Eurotunnel Le Shuttle, which runs vehicle-carrying trains from Folkestone.
The disruption started about midday and at least 30 Eurostar trains were cancelled, with many turning back to where they started.
Eurotunnel later said management and trade unions had reached a deal that meant services would “resume progressively this evening and Eurostar tomorrow morning [Friday]”.
Getlink, the company that manages Channel Tunnel infrastructure, said unions wanted three times the €1,000 (£866) bonus they were offered.
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The problems came on a day when all services from London Euston were suspended for a time due to overhead line damage near Watford Junction.
King’s Cross also had severe delays due to a fallen tree in the Newark area.
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Large crowds massed outside the stations and on concourses, staring at their phones and trying to work out alternative routes.
At 4.30pm, Euston said the problem had been fixed and “we are working closely with train operators to get you on the move”.
However some operators, such as London Northwestern, were still reporting disruption on Thursday evening.
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Plane struggles to land in Storm Pia
Storm Pia also disrupted air travel, with some planes diverting from northern airports and British Airways grounding two dozen flights.
Video showed a pilot fighting to land his plane at Birmingham in 50mph crosswinds.
The aircraft was less than 100ft from the tarmac when it was forced to pull up – but it made it down safely on the second try.
Gusts of 115mph were recorded at Cairngorm Summit in the Highlands, while Brizlee Wood, near Alnwick in Northumberland, saw 81mph.
About 40,000 households were affected by electricity outages in the North East, Yorkshire and northern Lincolnshire.
But nearly all were reconnected by Thursday evening, said operator Northern Powergrid.
Elsewhere, a man was taken to hospital with non-life-threatening injuries after a tree hit his car in Clifton, Derbyshire. Police in the county said a number of trees had fallen on the road.
Storm Pia, named by Danish forecasters, is set to move towards mainland Europe where its effect is expected to be more severe, said the Met Office.