A baker’s dozen of Great British Bake Off contestants will be tasked with creating a fruit cake and a showstopper based on their dream childhood birthday cakes when the hit show returns for a new series.

The episode opens with hosts Noel Fielding and Sandi Toksvig, and judges Prue Leith and Paul Hollywood, dressed up as characters from the Wizard Of Oz, with Fielding sporting bunches, red glittery shoes and a blue gingham dress as Dorothy, Toksvig dressed as the Scarecrow, Hollywood as the Tin Man “who doesn’t have a heart” and Leith as the Lion, joking “I was late, it was the last costume”.

Marking the 10th series of the show, the episode includes a montage of previous winners including Nadiya Hussain, Candice Brown and John Whaite, as Toskvig says: “It’s our 10th anniversary, but who will be our 10th Bake Off champion?”

The Great British Bake Off 2015
Nadiya Hussain won the show in 2015 and has become a breakout star (Love Productions)

The inclusion of 13 contestants means two people could be axed at any point in the series, Hollywood adds.

The first signature challenge of the series sees the bakers tasked with creating the perfect fruit cake, but it is a bumpy start for support worker Dan, who decides to double his quantity of fruit at the last minute.

Theatre manager Michael is also challenged when a string of kitchen accidents leave him with half his hand bandaged, and online project manager Helena battles uncooperative caramel in her bid to create a perfect bat made of sugar.

The Great British Bake Off 2019
Helena struggles with caramel (C4/Love Productions/Mark Bourdillon)

The baking hopeful, who was born in Ceuta – an autonomous Spanish city on the north coast of Africa and raised in Lanzarote, prompts giggles during the showstopper challenge when Hollywood misunderstands her as she describes her “fairy garden” chocolate cake.

Other childhood dream cakes include a pop-up story book, a secret woodland based on book The Faraway Tree, a sweet shop, a pirate island and a rocket.

The line-up for the new series is the youngest in the show’s history and includes seven people in their 20s while the oldest contestant is 56, with an average age of 31 in the tent.

The Great British Bake Off 2019
Jamie is just 20 (C4/Love Productions/Mark Bourdillon)

In previous years there have been contestants in their 60s and 70s, and the majority of line-ups have had an average age closer to 40.

There are usually 12 amateurs in the Bake Off each year, with the exception of 2013 when 13 took part, and the first series in 2010 when there were just 10.

This series this includes geography teacher Alice, 28, fashion designer Amelia, 24, vet Rosie, 28, student Henry, 20, and shop assistant Steph, 28.

Also hoping to impress the judges is lorry driver Phil, 56, marketing consultant Priya, 34, and print shop administrator Michelle, 35.

The upcoming series will be the third to air on Channel 4 after the show parted ways with the BBC.

It will begin on Channel 4 on August 27 at 8pm.