Prue has said she is “mortified” to have ruined tonight’s final after she named the winner on social media.
"No one told me judging a #gbbo final would be so emotional, she wrote in a since-deleted message.
“I wanted them all to win. Bravo….” she added, before naming the winner.
Later, she explained that she is currently abroad and in a different time zone.
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“I am so sorry to the fans of the show for my mistake this morning,” she wrote.
Channel 4 bosses will no doubt be hoping that the slip-up doesn’t cost them viewers.
Poaching the Great British Bake Off from the BBC was seen as a risky gamble by many, but it has proven to be a worthy investment for the broadcaster.
The revamped series was regularly drawn in 8.9 million viewers, about 2 million less than it did on the BBC, but still more than any other Channel 4 show this year.
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
For those who are desperate to know, click here to find out who has won the Great British Bake Off 2017.
If you’d rather enjoy tonight’s episode spoiler-free, read on.
What time is the Bake Off final on?
The three finalists return to the Bake off tent for one last time tonight at 8pm on Channel 4.
Like every episode this year, the final will run for 75 minutes.
Sandi Toksvig and Noel Fielding will announce the winner shortly after 9pm.
Great British Bake Off: Prue, Paul, Noel and Sandi will announce the winner tonight
Great British Bake Off: Prue Leith spoiled the final by tweeting the winner's name today
What will the finalists bake?
For the final signature, the bakers will prepare a batch of loaves, followed by a biscuit bake technical.
The winner will be decided with a multi-layer patisserie showstopper.
How to watch the Bake Off final online
Fans can tune in to the final as it airs by visiting Channel4.com.
The episode will be available to watch on demand after it has aired.