Writer and actor Phoebe Waller-Bridge has revealed that a film she is collaborating on with her sister is the most exciting thing she has ever done.

The Fleabag creator revealed that her sister Isobel, a musician who wrote the score for the hit TV show, has a role in the secretive new project.

“I am totally obsessed,” Waller Bridge said. “I have never been so excited about writing anything.”

Her comments came at an event at the Southbank Centre’s Royal Festival Hall on Sunday night to discuss her new book based on the hit TV show – Fleabag: The Scriptures.

It would not be Waller-Bridge’s first film credit. She was brought in to help polish off the script for the forthcoming Bond movie.

She also revealed a desire to write another play.

Fleabag was originally staged at the Edinburgh Festival Fringe in 2013 before being adapted for a BBC series three years later.

Virgin Media BAFTA TV Awards 2019 – Arrivals – London
Phoebe Waller-Bridge was speaking at an event held at the Southbank’s Royal Festival Hall (Ian West/PA)

The second series introduced a character widely referred to as the “hot priest” by fans, who becomes a love interest for Fleabag – the show’s unnamed protagonist.

But Ms Waller-Bridge said she did not invent the term to refer to the character played by Andrew Scott.

“He is very much just ‘priest’ in the script – Twitter created ‘hot priest’, I believe,” she said.

But Waller-Bridge, who also stars as Fleabag, said she was nervous about writing the character.

“I was worried about writing a priest, especially a comedy priest,” she said, revealing that she was afraid of falling into some traps.

Published last month, Fleabag: The Scriptures contains the show’s script and new writing from Waller-Bridge.

The show started life as a 10-minute monologue at the Leicester Square Theatre in London, but was made into a full Edinburgh show after Waller-Bridge was accosted by a member of the audience afterwards.

The writer revealed that an “absolutely hammered” woman came up to her to demand she turn the short piece into a full-length play.

“That was so f****** good, you’ve got to take it to Edinburgh,” the woman said, according to Waller Bridge. “I was like ‘yeah, yeah’,” she said. “The next day Francesca (Moody, Fleabag’s producer) contacted the Underbelly.”