Earlier this year, it was announced that stage star Tyzack had been cast in the role of Lydia, who is Janine Malloy's estranged grandmother. Viewers saw her on screen for the first time last week as Janine (Charlie Brooks) visited her gran in hospital after hearing that she was unwell.
However, following Tyzack's unexpected departure from the soap, programme chiefs have recruited actress Heather Chasen to take over the part. Chasen has appeared in a number of TV roles since the 1960s, including appearances in Z Cars, Young Sherlock, The Bill, Casualty and Doctors.
EastEnders producers took the unusual step of recasting the role with immediate effect as the ongoing storyline between Lydia and Janine will be an important one for Albert Square in the months ahead.
Speaking of the decision, a show spokesperson told DS: "Unfortunately, due to a personal matter, Margaret Tyzack has had to finish filming earlier than planned.
"In order to continue the current storyline we've taken the decision for Heather Chasen to take over the role of Lydia."
Chasen will begin filming at EastEnders on Friday. The changeover will then take place on screen immediately, meaning that fans will see the actress's first scenes as Lydia next week.
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