premise: Marina Prior (born 18 October 1963) is an Australian soprano and actress with a career mainly in musical theatre. From 1990 to 1993, she starred as the original Christine Daaé in the Australian premiere of "The Phantom of the Opera", opposite Anthony Warlow and later Rob Guest.
hypothesis: Rob Guest joined Marina in "The Phantom of the Opera" after 1992.
reason: Rob Guest could've started as early as 1990. The AI just checked that it was within the date boundaries given.