Written by Sally Wainwright, the series stars Jacobi as Alan and Reid as Celia – a couple reunited after 60 years – alongside Sarah Lancashire, Nicola Walker, Tony Gardner, Dean Andrews and Rupert Graves.
On Sunday more than 6m viewers saw the third series come to an end with the marriage of Alan’s daughter Gillian (Walker) and former brother-in-law Robbie (Andrews).
BBC bosses have now confirmed the show will return for another series.