She first appeared as the opinionated mini-skirt wearing character in a stage version of the sitcom. Marina was an instant hit with the audience, resulting in writer Roy Clarke deciding to incorporate her into the TV series.
She first appeared on screen as the peroxide blonde in 1985, and soon became involved in a long-running affair with Howard, played by Robert Fyfe. In total, she appeared in 216 episodes of the gentle comedy until it was cancelled in 2010. At its peak, the show attracted over 18 million viewers.
Fergusson's other TV appearances include playing various characters (most recently Dorothy Hoyle) in Coronation Street, and roles in shows such as Crossroads and Doctors.
Born in 1944 near Wakefield, she trained as an actor at the Royal Welsh College of Music and Drama and was soon in much demand as a stage actor.
She took on a number of stage roles across her career. Notably, she was nominated for an Olivier award in 1998 for her portrayal of Hylda Baker in her show She Knows You Know!. She also wrote a biography of the music hall star.
Appearing on a celebrity version of the quiz show Pointless in 2017, she spoke about her character's skimpy outfits in Last Of The Summer Wine. Talking to the hosts, she said: "When I got - shall we say - a little bit older, it wasn't quite the same getting all dressed up in the morning in a pair of little mini shorts and a very low-cut blouse. But we battled through. We got on the bike and off we went."
In 2014, Fergusson sold the bike her character rode, making £500 at auction. Explaining she was moving from Yorkshire to a London address which had no place to store it, she said: "If I could have kept it, I would have done, but I'll let some wonderful fan have the pleasure of it."
Her agent confirmed her death this morning, although the cause was not given. The Daily Mail reports that she was said to have been ill when friends saw her at the weekend.