Earlier this year, it was announced that Hattie would be joining the cast of the coming-of-age drama from season 13, playing a character named Libby Guthrie.
Sharing a photo on her Instagram story of Hattie's name on a card at a table reading, Sally tagged her daughter and the Waterloo Road page while writing: "So excited for this."
This isn't the first time that Sally, who has played Sally Metcalfe on the cobbles since 1986, has shared her excitement over her daughter's first acting role.
Following the unveiling of Hattie's character Libby in June, the actress shared the news in a post on her Instagram, writing: "So proud of you @hattiedynevorr joining @waterlooroad playing Libby Guthrie. Such a fabulous cast and crew."
Hattie isn't the only member of her family to have starred on the show either, with her older sister Phoebe Dynevor landing her breakthrough role on the series back in 2009. She has gone on to star in hit Netflix series Bridgerton and the upcoming film Fair Play.
Meanwhile, Waterloo Road was recently confirmed to have been renewed for two more seasons after its upcoming season 13.
"We're beyond thrilled with the triumphant return of Waterloo Road, and so thankful to the BBC for committing to the show so fully," executive producer Cameron Roach said of the news.
"We love that the show has the potential not only to be a crown jewel for BBC iPlayer, but also serve as a true beacon for training, and inspiring next generation talent."
Waterloo Road will return for its 13th series on BBC One and BBC iPlayer.
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