The character debuted on-screen during the episode airing on 2 August 2010 and was introduced by series producer Paul Marquess as a member of the yet to be established Costello family.

Originally introduced as Jasmine, the character eventually reveals that he wishes to be known as Jason, and legally changes his name.

In January 2010, it was announced that Lucy Allan had stepped down from the position of series producer and that Paul Marquess had taken over the role.

[6] In September 2011, it was announced that Atkin had decided to quit the programme in order to pursue other projects.

When the character was announced, two pictures were released showing Victoria dressed as 'Jasmine' and true, male self, Jason Costello.

[8] Of the character's creation, Digital Spy reported that "Jasmine's journey will highlight the mental trauma, physical disgust and ongoing frustration of a boy trapped in a girl's body, as well as the effects that [his] condition has on those around [him].

[8] Atkin also revealed she had drawn inspiration from Hilary Swank's performance as Brandon Teena in the film Boys Don't Cry, but stated that the storyline would not progress in such a violent way.

[8] Whilst interviewed by newspaper The Guardian Atkin admitted she had not known anything about transgender issues before taking the role and stated: "It was a big revelation for me how much taunting and bullying there is.

Executive producer also claimed that the storyline was not aimed to be sensationalist or being used to increase viewing figure, stating he grew up knowing what isolation felt like and wanted to portray a story which mirrored a taboo subject that people would find hard to talk about to their peers.

When Jason first arrives he shows anger to his half sister Jem for running away from home in 2007.

Jason is taken to Evissa by his mother for a makeover and he seems unhappy to be there, until he strikes up a friendship with Bart McQueen (Jonny Clarke).

Sometime later, Bart tells him about stealing Jacqui McQueen's (Claire Cooper) money in a bid to impress him but is shot down by his disgust.

Things take a turn for the worse when Jason reveals that he still fancies boys and knocks back Fern's advances.

After hearing Jason's reason for stepping in front of the car, Bart confronts Heidi Costello.

After Bart decides not to sit his exams, Jason helps him revise and Sinead becomes jealous.

When they break into a farmhouse for food, the property owner locks Jason and Bart in a cellar.

She rips Jason's clothes off and degrades him for wearing chest bandages and tells him he will never be a real boy.

Jason is arrested after he steals Ash Kane's (Holly Weston) and later buys unprescribed treatment via the internet.

Jason then says an emotional farewell to Bart, Sinead and Tilly Evans (Lucy Dixon) and all his family.

Jason says that he wants to start again in America as if Jasmine never existed and he says "I will never forget you Bart McQueen".

[10] Jason's transgender storyline was nominated in the Radio Times Creative Diversity Network Soap Award.