A Royal Mail injunction to stop next week's postal strikes will be heard at the High Court tomorrow.
Evidence will be presented at a hearing starting at 10.30 in front of Mr Justice Supperstone.
Royal Mail and the Communication Workers Union (CWU) will present their cases in the hope that a decision can be reached by the court tomorrow. This will either open or close the door for industrial action to go ahead.
On Monday Royal Mail filed a legal challenge to prevent a 48-hour walkout scheduled to start on 19 October. It says planned industrial action is "illegal" and cannot go ahead before both sides have attended five weeks of mediated talks.
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The CWU, which represents 110,000 Royal Mail staff, disagrees. It says a mediator has been present at prior talks.
Both sides signed up to an "Agenda for Growth" side agreement in 2014 within which Royal Mail agreed to concede some its rights as an employer in order that further talks take place in the event of a union giving notice of industrial action.
The union is striking over a raft of planned changes, including closing Royal Mail's "gold-plated" final salary pension scheme and changing working practices.