Apple CEO Tim Cook will testify today - Friday 21 May - in the ongoing lawsuit between Epic Games and Apple.

Cook is expected to defend Apple's corporate policy that all apps must meet certain criteria to be available via the App Store, Cnet reports. Epic, meanwhile, argues that the enforcement of these rules has given Apple an illegal monopoly (a portrayal Apple has rejected).

Cook is expected to answer questions from lawyers representing both Apple and Epic, as well as the judge. His testimony comes towards the end of the three-week trial.

Many of Apple's most visible executives have already taken the stand. Earlier this week Phil Schiller revealed the cost of WWDC among other revelations, and Craig Federighi has also appeared. But Cook is the biggest fish of all.

The CEO's testimony is scheduled to begin on Friday 21 May at 4pm UK time. The testimony is expected to take up the entire day.

Anyone who wants to can listen directly to the testimony by calling +1 877 336 1839 to the US and entering the access code 9403112. Please note that this can be very expensive.

No recording of the testimony will be published as this is not allowed.

This article originally appeared on Macworld Sweden. Translation by David Price.