ET spoke to the 57-year-old actor on Tuesday to talk about his miniseries, A Very English Scandal, where he also chatted about tying the knot with Eberstein in London last month. The two have been romantically linked for six years and share three children together. Grant also has two children from a previous relationship.
"It was a nice thing to do," Grant said of getting married. "I feel [it was] definitely the right decision. I'm very lucky. Great person."
As for what type of wedding it was, Grant said it was incredibly private. On May 25, the couple was snapped outside the Chelsea Register Office in London with friends and family, just days after their engagement was revealed via an official notice of their planned marriage being posted on display at the local town hall.
"It was a minuscule wedding, there was almost no one there," he shared. "But lovely, yeah."
As for avoiding any over-the-top pomp and circumstance, Grant cracked, "I left that to Harry and Meghan."
These days, Grant is busy promoting his new project, which is based on real-life British Liberal Party leader Jeremy Thorpe. Thorpe was tried and acquitted of conspiracy to murder his gay ex-lover in 1979.
"I haven't done a real-life person who a lot of your audience is going to remember," he said of the challenges of playing Thorpe. "They won't in America, but Britain, a lot of people kind of over 45 remember this guy. Then you're confronted with a problem of, do I do an imitation or do I do a performance? Or do I do somewhere in between the two? And I ended up doing somewhere in between the two."
"I watched a lot of footage of him through YouTube and things, and found that I could imitate him and thought, well, it'll just be an imitation and very shallow, so then I read every single piece of literature on the guy and met lots of his friends, his colleagues," he added. "I sort of went deeper and deeper and hopefully it's a person."
Grant said he now considers the project the biggest success of his career.
"Crazy because now the thing's out in Britain and it's been really the biggest success of my career, and I can't believe I managed to find nine reasons not to do it," he said of initially being wary of playing the role. "But there were very good reasons to do it, obvious ones. It's a great part. It's a fascinating piece of history -- sort of almost too good to be true. It's just so weird that this actually happened."
Amazon Prime original A Very English Scandal debuts exclusively on Prime Video on Friday, June 29.