BBC One is currently airing the long-awaited season three, the final instalment of Sally Wainwright's drama about a police battle against Yorkshire's drug problem, and fans feel that the series has lost none of its brilliance during the eight years it was off air.
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Lancashire plays a police sergeant trying to avenge the death of her daughter, who took her own life after being raped by violent drug dealer Tommy Lee Royce (James Norton).
Catherine and her sister Clare (Siobhan Finneran) are now bringing up grandson Ryan (Rhys Connah) who has been making contact with his imprisoned father in season three.
Admirers of Lancashire's performance included TV presenter Anita Rani, who tweeted: "I’m already sad it’s going to be over. It deserves every award. And is there a more powerful female character on Tv than Catherine Cawood. @SarahLancsUK you are outstanding."
One fan posted a scene of Lancashire crying as her character Catherine and wrote: "This tear needs its own BAFTA."
The praise also rolled in for series creator Wainwright, and Lancashire's co-star Finneran.
One viewer tweeted: "That was PHENOMENAL. 15 minutes of pure talent. Not one raised voice. Sarah and Siobhan absolutely gave everything during that and Sally gave them the most amazing material to work with."
Someone else agreed: "So good! Two of the best actors we’ve ever had."
Another fan wrote: "The way Sarah Lancashire can flip between tragedy and comedy and back again in half a beat is genuinely incredible. And it’s surely the result of an astonishing talent honed on Coronation Street."
Someone else added: "I’m in constant awe of the way Sarah Lancashire delivers dialogue. Some actors you can see acting. Not her. Entirely believable, always."
The whole of season three so far has delighted viewers, who feel it was worth the long wait.
Last week, famous fan Anneka Rice tweeted: "I loved Happy Valley so much on Sunday I’m watching ep 2 again. Might even go for a third session. Masterclass of acting. That scene where @SarahLancsUK meets the Head Teacher…."
Someone else wrote: "Sarah Lancashire needs to be spoken about in the same way Olivia Coleman is."
Happy Valley continues on Sundays at 9pm on BBC One.