Casualty has announced that Tony Marshall, Charles Dale and Richard Winsor are all returning to the show for its 35th anniversary celebrations later this year.

The medical drama will mark the milestone birthday in September and to celebrate, the show will air a special flashback episode that promises to 'set in motion a chain of events which changes the course of the future for some of the staff'.

Winsor's Cal and Marshall's Tony have both previously been killed off in the show, while fan favourite Big Mac (Dale) left in 2016, suggesting that the episode will be set at least five years in the past.

Marshall's real-life son will also appear in the episode playing a young boy who needs help from the emergency department, and new character Stevie (Elinor Lawless) will be introduced.

"It was strange to come back but rewarding at the same time as the episode tackles yet another important subject," said Marshall.

"It was a joy working with my son as well as of course Charlie Dale and Richard Winsor. We had to abide to COVID restrictions which is not easy but we did it. The audience are going to love the episode!"

Series producer Loretta Preece added: "There is a 35th anniversary smorgasbord to offer both new and old fans of Casualty with huge stunts, faces from the past, some indelible new characters and some wonderful story twists.

"Elinor Lawless as new consultant Stevie makes a splash right from her first episode and I am confident she will become one of the most talked about characters in Casualty's history.

"There are huge, heart-breaking stories for Ethan and Jacob later in the series and I'm delighted to also announce a wonderful two-part special to be written by Barbara Machin, one of television's most prestigious writers, for Christmas 2021."

The anniversary episode will air "later this summer" on BBC One.