Possible Clues:

• Not probable, really the reverse
• Not at all probable
• Odds against posh cathedral town being on the back burner
• Remote, universal link, possibly, with Cathedral?
• Tall, up-market fire faces office of bishop
• The improbable combination of Lukey about nil
• Doubtful
• Hardly going to happen, improbable
• Improbable as Gray's stories, mostly
• Having little chance of being the case