Now married to her Sense & Sensibility co-star Greg Wise, the beloved Brit tells TV Times magazine that her six-year marriage to Branagh was doomed because she was very demanding.
She says, "I'm a bit bossy, and I have to say some people find it quite difficult to deal with. Mentioning no names, but my first husband."
The actress also tells Britain's Sunday Times that she has nothing but love for Helena Bonham-Carter, her Howards End co-star, who came between herself and Branagh at the end of their marriage almost 20 years ago.
She adds, "(It's) all blood under the bridge. You can't hold on to anything like that... It's pointless. I haven't got the energy for it. Helena and I made our peace years and years ago."
Branagh and Bonham-Carter briefly dated after he split from Thompson, but they broke up in 1999 and the actress went on to romance director Tim Burton.
Thompson admits she wasn't surprised when her ex and her former co-star became an item: "We are (alike), being slightly mad and a bit fashion-challenged. Perhaps that's why Ken loved us both. She's a wonderful woman, Helena."