Martin Freeman said that "it was not that much fun," the film Sherlock with his former partner Amanda Abbington while they were in the process of grinding.
Couples who have been together for 16 years and have two children, star together in the BBC show as a married couple, John and Mary Watson.
Freeman confirmed the end of their relationship in December 2016.
He told BBC Radio 4 disc desert island: "We met on a film set in 2000, we met on the Channel 4 drama called Men Only and we clicked immediately.
"We just hit it off, we went on a date a day or two later, and we were together for 16 years.
"It was and remains one of my favorite actors, I think it is a fantastic actor."
On the question of how it was to work with her at Sherlock, he replied: "Awful! No, it was good, I really love to work with her.
"By the time the last Sherlock, what we did, we were kind of in the midst of crushing, so it was not much fun, but if we were not in this environment, it was great."
Freeman said that he thinks that they share parenting "very good, actually," adding: "I always knew that the people who broke can be civil and do this for the children, it's all right.
"I do not just want to be nice for the children, I would be polite to us, because if you love someone that long, and they were neodymium & # 39; emnay part of your life, that – that is not supposed to count now! ?
"It just does not make sense to me, so that we do, we do, and I think that the kids see us get on well, they just love the same two people in a different geography now."
Freeman starred in Sherlock's opposite Benedict Cumberbatch in the title role, since 2010, and said that the proportion of couples chemistry "is rare, and, of course, it is even rarer to be picked in the public way."
He added: "Probably nothing I did, maybe nothing that I ever will do, does not resonate with certain parts of the world's population as well as Sherlock, he just hit a lot of buttons for people.
"The reaction can be quite intense. So by the time we filmed the last of them had some supporters who were so adamant that John and Sherlock were gay, they know it and they know that Steven (Moffat) and Mark (Gatiss) going to write an episode where we held hands in the sunset together, and therefore, if it did not there was a piece pf people going "This is a betrayal."
"Let's just say, they invest a lot in it, and to a certain point, that is beautiful. For some time, it's more complicated. "
Desert Island Discs on BBC Music and BBC Radio 4 on Sunday at 11.15am.
– Press Association