Robert Lindsay and Zoë Wanamaker have both agreed to star in seasons eight and nine as well as a Christmas special – a total of 20 new episodes.
Pauline Quirke and Anna Chancellor have also agreed to make guest appearances in the new series.
The show regularly attracts audiences of up to 7 million people to BBC One, despite being largely ignored by critics.
Don Taffner Jr, one of the show’s executive producers, said: ‘For the BBC to commission so many episodes is proof of their on-going commitment to this consistently top-rated comedy.’
