Possible Clues:

• Firm adopting advertising is showing incredulity
• Disorganised purser is a turn up for the books
• One’s not expected America to back British pronunciation to increase
• Unanticipated occurrence
• Purser’s upset about one unexpected revelation
• Stagger from drink increase round mid-afternoon
• Drink noisily, tossing off a litre — get up, then stagger
• In dawn run, philosopher's first to overcome new shock
• Sudden astounding event
• On leaving jail, seized by certain shock