Sykes had the same premise as Sykes and A... with Sykes, Jacques, Richard Wattis and Deryck Guyler reprising their former identical roles. The series was brought to an end by the death of Hattie Jacques of a heart attack on 6 October 1980.
With the same premise as Sykes and A..., unmarried twins Eric and Harriet (Hat) Sykes are now living at an end of terrace house, 28 Sebastopol Terrace, East Acton, two doors down from their house in the previous programme. As before, Eric is childish and accident-prone while Hattie is patient. Their neighbour is the snobbish unmarried Charles Fulbright-Brown, and PC Corky Turnbull is the local policeman. Corky's wife, Elsie, is unseen, except for one episode, Caravan, in which she appears with her face covered in porridge during a food fight between Corky and Eric. Deryck Guyler also played Corky's brother Wilfred Turnbull, a train attendant on the Glasgow to London sleeper train, in the episode Journey.
Following the death of Richard Wattis in 1975 a new neighbour, Melody Rumbelow, moves in. The local baker is the widowed Madge Kettlewell (Joan Sims), who appears occasionally, and who fancies Eric - she is first seen in the episode Football. Eric and Hattie are also the owners of a cuckoo clock, naming the very temperamental bird inside Peter. Both speak to it as if it were a real bird, and a great deal of comedy derives from the antagonistic and sarcastic 'conversations' between Eric and Peter.
The first series of Sykes was released on DVD in the UK (Region 2) in 2004. Several episodes in this set were reassembled from the original studio sessions rather than the broadcast masters. This not only yielded better quality, but also allowed scenes that had been cut for timing purposes to be restored, and for outtakes to be included as extras. Conversely, since the colour videotape of the episode "Journey" had been wiped this episode was taken from a black and white copy. A brief featurette explains some of the restoration techniques employed.
A Complete Series DVD set (containing all 68 episodes) was finally released on 26 June 2017.