Royal Mail boss Moya Greene will lead talks with the firm's main union in the hope of breaking the deadlock in a long-running industrial dispute that threatens a Christmas shutdown.
The Communication Workers Union (CWU) and the postal giant have agreed on the appointment of a mediator to oversee seven weeks of talks.
Professor Lynette Harris, a deputy chair of the government's Central Arbitration Committee, will oversee matters.
The latest round of talks come after the CWU was forced to back down from a 48-hour walkout earlier this month.
Royal Mail successfully challenged strike action in the High Court on the grounds that both parties had signed up to a side agreement that stipulated mediated talks must go ahead prior to any industrial action taking place.
The CWU said mediators were a present at months of previous talks which finally broke down in early September. It said it held its first face-to-face talks on the matter last week.
The union said it has voiced "concerns about the delay" in appointing a mediator in a letter to its branches yesterday.
With talks set to kick off tomorrow, the union will be unable to strike for nine weeks thereafter. The side agreement – called the "Agenda for Growth" – stipulates seven weeks of mediated negotiations must take place. By the law, the CWU would then have to provide Royal Mail with two weeks' notice before holding industrial action.
Workers are aggrieved by a Royal Mail decision to close its mammoth pension scheme and alter key working practices.
Royal Mail says the pension scheme closure could lead to annual costs spiking to over £1bn. And with its largest division, letters, in seemingly terminal decline it wants to better challenge in the parcel sector. To do so, it needs to change certain practices – for example, rejigging working hours – to compete with next-day delivery rivals such as Amazon and Hermes.