With less than 12 hours to go until the Great British Bake Off 2017 champion is revealed, Prue tweeted the name of the winning contestant.
"No one told me judging a #gbbo final would be so emotional. I wanted them all to win. Bravo….” she wrote, before naming the winner.
Prue deleted the spoiler, but not before Twitter users caught a glimpse.
Great British Bake Off 2017: Sophie Faldo accused of benefit fraud
Great British Bake Off 2017 winner SPOILED by judge Prue Leith
Many were understandably outraged, with one fan writing: "Have you just ruined the GBBO final?"
Another fumed: “Prue Leith man what a joke thought I was safe on Twitter until later.”
Many joked that former judge Marry Berry was behind the slip-up.
— Metro Radio News (@MetroRadioNews) October 31, 2017
Great British Bake Off: Prue Leith has tweeted the winner of tonight's final
Mary made a similar mistake in 2015, when she revealed the name of a contestant who hadn’t yet been eliminated.
“We’ve lost three,” she told BBC Radio 2’s Chris Evans.
“We lost Marie last week, Dorret and on the first week it was our lovely chap with his little hat on Stuart.”
At the time, fans didn’t know that Dorret had left the show.
Prue returned to Twitter to apologise, and explained that she is currently abroad and in a different time zone.
“I am so sorry to the fans of the show for my mistake this morning, I am in a different time zone and mortified by my error,” she wrote.
For those who are dying to know who has won, Express.co.uk has hidden the spoiler on the flip card below. Proceed with caution.
Will Kate win Bake Off?
Kate also had an impressive start, winning the very first technical challenge in week one.
But out of all the finalists she has won the star baker the least, coming top just once in week four.
In the semi-final Kate’s rainbow meringue centrepiece made her a serious contender for the top spot, but she was pipped by Sophie in the end.
Our guess: third place.
Great British Bake Off: Kate won the very first technical
Great British Bake Off: Steven won star baker in the first two weeks
Will Steven win Bake Off?
Steven started off strong in the competition, winning star baker in the first two weeks.
But his early confidence began to veer on cockiness, and he was regularly told off for putting style above substance.
He brought it back in week seven, winning star baker for the third time for his Sicilian-style sfogliatelle, but came close to elimination in last week’s semi-final.
Our guess: second place.
Great British Bake Off: 2017 contestants revealed
Wed, August 30, 2017
From a former artillery officer to a 19-year-old student, meet the contestants for the 2017 edition of the Great British Bake Off as it makes its debut on Channel 4
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The judges and presenters for The Great British Bake Off
Great British Bake Off: Sophie has won two technicals and two star bakers
Will Sophie win Bake Off?
Sophie is by far the strongest technician out of the final three, with two wins and two second places.
In all but two series so far, the person with the strongest technical scores has won the competition.
She has also won star baker twice, and has made it through the competition without landing in the bottom of the pack.
Our guess: winner.