Ross Kemp has admitted he struggled to learn his lines when he returned to EastEnders following a decade away from the soap.
The award-winning documentary-maker is reprising the role of Grant Mitchell ahead of the on-screen death of the hardman's mother, Albert Square matriarch Peggy Mitchell (Dame Barbara Windsor).
The actor - who has received international recognition for his series Ross Kemp On Gangs - told the Radio Times: "I've been too busy dodging bullets in real life.
"So, to start with, learning lines was like pouring treacle into my head."
Ross, 51, last appeared on the BBC soap in 2006 and said it was "surreal" going back to Walford.
He said: "Having spent 10 years doing something that couldn't be further removed from EastEnders, I sat in my dressing room, thinking, 'I've finally flipped.' It was surreal.
"Being the age I am, I fell asleep one lunchtime, woke up and thought, 'Where am I?' It was like one of those dreadful American soaps: 'It's all been a dream! You weren't really in Afghanistan making documentaries. You were in Borehamwood the whole time'."
The actor said he had "a bucket-load of mixed emotions" about returning, as it reminded him of some hard times.
"There was a lot of warmth there," he said. "But it does bring back memories of dreadful times in your personal life, too. My grandparents died when I was on that set. I got to go to the funerals, but I should have been with them when they were in hospital, and I wasn't."
EastEnders stalwart Peggy is battling cancer and her exit episode will air on May 17.
Ross said shooting his final scenes with Dame Barbara, 78, has been emotional.
"She's saying goodbye to Peggy, who - apart from her roles in the Carry Ons - will be the definitive character that she plays in her lifetime.
"So, ultimately, it's about paying tribute to Barbara, who's an iconic human being, both on and off screen," he said.
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