The actor, who has been appearing in the role since November, explained that he wants to keep challenging himself by exploring different sides of Derek's personality.
Writing in his new autobiography Gangsters, Guns and Me - which is being serialised in The Mirror this week - Foreman commented: "We hit the ground running to bring Derek to the Square and Pam St Clement was phenomenal.
"In one scene, she established my character more easily than I could have done in four episodes. To see Pat, who's never been frightened of anyone, running scared of this man showed everything about my character in a moment."
"We've got plans to take Derek off in an interesting new direction, which will be a real challenge for me as an actor," Foreman added. "It would have been so easy to go in there and do the one-dimensional gangster who growls at everyone, but I care too much about showing the real side of these characters.
"For the moment, EastEnders is where I'm at and I'm loving every moment of it. I've never been recognised so much in my life and I get stopped all the time in the street - it's nuts. Every day's a challenge."
Derek previously appeared on screen briefly in 1996, with actor Terence Beesley in the role.
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Watch a behind-the-scenes EastEnders video featuring Jamie Foreman below: