The London Metal Exchange is seeking £250,000 from the Office of Fair Trading to cover costs incurred from challenging the competition regulator's unprecedented three-month ban on extended opening hours.
The Competition Appeals Tribunal met in London this week to hear submissions from both sides and has retired to consider its verdict.
Earlier this month the LME, the world's largest metals exchange, finally extended its electronic trading hours to capture lucrative business in Asia after the OFT lifted its ban.
The change of heart was prompted by an about-turn by Spectron, the operator of a rival electronic trading system that had lodged the original complaint against the LME in July 2003, a year before the OFT launched an inquiry.
Spectron, chaired by the former Conservative sports minister Lord Moynihan, had claimed the LME plans to extend its hours were designed to drive its operation out of business. That claim was withdrawn in March, and Spectron called on the OFT to lift the ban.
From 1 June, trading on LME Select, the screen-based dealing system, was extended by six hours to run from 1am to 7pm.