The owner of Southern Railway has launched a last-minute bid to halt a series of crippling strikes by train drivers.
Members of the Aslef union are due to walk out for three days this week and on six consecutive days in January in a bitter dispute over driver-only trains, which will halt all Southern services and affect hundreds of thousands of passengers.
Owner Govia Thameslink Railway (GTR) has argued that the action, which is lawful under English domestic law, would unlawfully restrict freedom of movement provisions under EU law.
On Monday, three judges in the Court of Appeal were asked to overturn High Court judge Sir Michael Burton's refusal to grant an injunction blocking what GTR has called "unprecedented" strike action.
Lord Justice Elias, sitting with Lord Justice Lewison and Lord Justice Lloyd Jones, said they would give a decision at the end of the hearing, which is likely to last all day.