Casualty fans have been given their first look at actress Cathy Shipton's return in a new clip of the show's 1,000th episode.
The milestone episode about Holby City Hospital's emergency department (ED) will be broadcast this Sunday on BBC One.
Cathy, who plays Lisa "Duffy" Duffin, featured in the original cast when the medical drama launched in 1986.
In the new video, Duffy has taken a telephone call and is heard saying: "ED? Yes, I think I can remember the way." Towards the end of the dramatic clip, she asks Doctor Gardner (Jaye Griffiths) to make a snap decision about a patient in a critical condition.
London-born Cathy spent 17 years in Casualty and has long been a favourite with viewers. She made a brief return for the show's 20th anniversary in 2006 before popping up again in 2015.
Ahead of her permanent return in August, this Sunday's episode will fill in more details about Duffy's life away from England.
Duffy will reconnect with her old colleague Charlie Fairhead (actor Derek Thompson who is also a member of the original cast), and reveal why she left her family in New Zealand.
Talking about her forthcoming comeback, Cathy told the BBC: "After returning last year for episodes one and two of series 30, many asked if Duffy was sticking around long-term.
"Well, the response was so positive that I've stepped right through and am thrilled to be back on the show."
She added: "The future looks very exciting for Duffy both professionally and personally, and I am equally excited to be working with such a talented and creative team of actors, writers, directors and producers."
Casualty actor Charles Venn, who plays nurse Jacob Masters, recently hailed the forthcoming 30th anniversary special.
The adrenalin-charged 110-minute episode will be broadcast soon.
"I don't want to give anything away, but my character Jacob is an integral part of it," he said.