The music mogul riled his fellow judge with a joke aimed at her ex-husband, Les Dennis, which came after one act arrived on stage with a t-rex puppet at this weekend's London auditions.
Addressing the performer, Amanda joked: “I can see the dinosaur winking at me, it’s flirting with me. It’s not the first time I’ve been flirted with by someone prehistoric.”
Unable to let the opportunity for a dig at Amanda’s personal life to pass him by, Simon then responded: “Leave Les alone”, referencing her prior marriage to the British TV personality, who is 18 years her senior.
A shocked Amanda then threatened to throw a glass of water over Simon, which would be the fourth time that weekend it had happened.
This isn't the first time that Simon took a dig at Amanda’s ex-husband, though.
Back in 2013, when Amanda remarked to another act that she’d gone “from rags to riches”, Simon laughed: “You’ve gone from Les Dennis…”
Earlier in this year's audition process, Amanda threw, not one, but three separate glasses of water over him, temporarily grinding production to a halt, and, as Simon noted, “ruining a microphone” in the process.
Last week, Amanda told HuffPost UK that she’d had a changed of heart about leaving the judging panel at the end of the upcoming series, despite claiming last year she thought the 10th series of ‘BGT’ would be her last.