EASTENDERS’ Kat Slater will explode with rage after discovering Hayley and Alfie Moon’s secret snog.

Actress Jessie Wallis, who plays the fiery mum-of-two warned viewers that Kat would “go crazy” after learning of their betrayal.

In tonight’s nail-biting episode, Hayley and Alfie are caught snogging by Stacey Slater.

She manages to keep her nerve and stays quiet, leaving Kat to discover the shocking betrayal for herself.

Talking about the explosive scenes, which will air on Christmas Day, Jessie told The Mirror: “It’s something that Hayley does.

“Obviously Kat is going to find out and she reacts in the way only Kat can react. She goes crazy!

“She’s so angry and upset, there’s this whole whirlwind of emotions that she’s going through and she just doesn’t care. There’s no vision, Kat’s just so angry and betrayed.”

And the kiss isn’t the only shock coming Kat’s way, as she will finally discover that the father of Hayley’s baby is Alfie – a secret viewers have known for months.

Jessie added: “[Kat] has been completely betrayed by not only her husband but someone in her family too.”

Speaking about his Christmas kiss with Hayley, Shane Richie, who plays Alfie, told Digital Spy: “Hayley starts to get cold feet about everyone being together and Alfie playing happy families.

“Alfie thinks she’s about to lose it and he says: 'No, we’ll get through Christmas and then we can sit down and find a way through it'.

“Stacey reads more into it. What she didn’t hear was the previous conversation when Hayley goes: 'Come on Alfie, you know you want me'. So Alfie, just to keep the peace, kisses her.

“The audience knows full well that he’s trying to do it to keep everything on track.

“But Stacey thinks something else and that ignites the fire. It all starts snowballing from there.”