The 54-year-old actor shared his equation with Hurley when he appeared on TV show Watch What Happens Live with host Andy Cohen, reports mirror.co.uk.
A segment in the show has guests answer three questions with the option of staying silent for one, or pleading the fifth.
When asked about his romance with Hurley, Grant didn't back out and instead gushed about her when asked why it "didn't work".
He replied: "You see the funny thing is, it did. She's still my best friend. The sex bit probably fizzled out but she's my absolute best friend. The number one person I call in a crises, so it didn't fizzle."
The Notting Hill actor Hugh dated Elizabeth for 13 years before they finally went their separate ways in 2000.
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Home/Entertainment/The Sex Bit Fizzled Out, She's My BFF: Hugh Grant On His Ex Liz Hurley