Pam St. Clement says some of the "EastEnders" cast used to "get upset" by Leslie Grantham's actions because he "didn't behave particularly well".
The former "EastEnders" star has revealed her late co-star - who passed away last month aged 71 - used to "test" some of the actors out with his antics, and once referred to her as a "great white whale", but she knew he was only joking and called him a "naughty boy".
Pam - who played legendary character Pat Butcher on the BBC One show - said: "That [Leslie's death] was a heck of a shock actually. I was never particularly close to Leslie apart from in a work sense.
"He was a devil you know, he'd test you. If you didn't pass the test then that was it, he left you to your own devices.
"But I remember one time, we were joking about and I walked into the Vic and he was there and he said, "Oh hello, it's a great white whale."
"But then I could see him go [laughing], and I was thought, "Yeah you were just waiting to see how I'd reacted weren't you? You naughty boy?"
"Had I got all uppity and then said I'm not speaking to you again, or whatever.
"There were people who used to get upset by Leslie, because he didn't behave particularly well, but there we are."
Pam admitted it was "very sad" when she heard Leslie - who was best known for his time on the soap as "Dirty" Den Watts from 1985 to 1989, and then again from 2003 to 2005 - had passed away because he was "under a cloud" after he departed the show.
Speaking on "Loose Women", she added: "It's very sad that he's died and it's very sad that he died because he was in a dire circumstance after he left "EastEnders", under a cloud somewhat. I'm afraid to say.
"Nobody should have to pay for their misadventures by dying. And I'm sorry for that and I'm sorry for his family."