Derek Milligan actor warns of 'tragic twist' in Corrie Christmas special

Liverpool-born Craige Els, who has appeared in Call The Midwife, Ripper Street and The Bletchley Circle, warned that Derek will become an "accidental villain" in the festive episode.

Drunk and desperate for revenge on the villainous Gary Windass (Mikey North), Derek will be at the heart of the episode's much-anticipated armed siege.

Gary invited Derek into his loan shark business but fearing he might expose his underhand dealings, took him hostage long enough to ensure he missed his flight to Florida for a family holiday at Disneyland, ruining his chance at salvaging his failing marriage.

"Gary has created a very dangerous beast, when someone has nothing to lose they will do extreme things and he wants revenge.

"He gets a text from his wife saying he will never see his kids again, his world has fallen apart and he has nothing to lose.

"Add the drink to that and the discovery of the gun, anything could happen."

By Christmas Day Derek is convinced Gary has ruined his life.

He finds a loaded antique rifle in a furniture shop and follows Gary into the Rovers Return before firing a shot to scare to customers.

Gary lures Derek outside and into a winter fairground set up on the street, and the pair face a dramatic denouement.

"He just wants to scare Gary," he said.

"He wants to see Gary as scared as Gary has made him feel and for once have the upper hand.

"What he doesn't anticipate is how far it could go and that's the tragic twist.

"It isn't a plot by him to go on the rampage on the street and kill anyone, he is not an evil man.

"He was once a powerful man and he has had all that power taken away from him by the one man who has now taken the most precious thing away from him.

"He has been pushed, he is broken and wild, but he is not evil, there is no malicious intent. There is no premeditation. He is not Pat Phelan or Richard Hillman, he is an accidental gunman, an accidental villain.

"Things snowball out of his control and he is devastated by what he ends up doing."

Els also revealed that he will be watching the episode on Christmas Day with his grandmother.

He said: "I have watched it for so many years, particularly with my nan Barbara.

"She is the biggest Corrie fan, she has watched it all her life. We never miss it.

"If I call by mistake when it is on she will literally not want to speak to me. The day I told her I had got a part in it, Christmas came early for my nan.

"I will watch it with her on Christmas Day and I can't wait to see her face when she sees what Derek gets up to.

"I have kept it all from her so it doesn't spoil it for her. She knows that he has the potential to be a bad character so she is looking forward to it."

The Coronation Street Christmas special airs at 8pm on Christmas Day on ITV.