Possible Clues:

• Mini show trials perhaps for those in various outfits preparing to make a play at this stage
• Pre-play activities
• They precede opening nights
• Mini show trials perhaps for those gearing up to practice their lines
• Mini show trials perhaps for those in various outfits preparing to make a play for the abbey
• Kind of code to pick up from top solicitor in genuine opening statement for show trials
• In the abbey, run through a few times with all the gear for show trials
• Dry runs, and a hint to the starts of 17-, 26- and 43-Across
• Show trials
• Final practice sessions