Keanu Reeves has been dating Alexandra Grant for "several years"

She told the New York Post newspaper's Page Six column: "I remember a couple of years ago, about a year and a half ago, [Alexandra] said, 'Keanu Reeves is my boyfriend,' and I'm like, 'Wait. What? What? What?'.

"It's really astonishing to me how in the last five months, all of a sudden, she goes to an event with him and everybody goes insane, like, 'It's his new girlfriend,'.

"She had gone to a lot of events with him [in the past]. It's just suddenly surfaced that he's been dating her for several years."

The 61-year-old actress - who met Alexandra at a dinner party many years ago - thinks her friend and the 'John Wick' star are a great match because they are both very low-key.

She said: "I saw him at her last art opening, and he's not, like, wanting the spotlight because he's a really low-key guy, too, and I think why everybody went crazy is that they're sort of the perfect couple.

"I think everybody wishes that they had something like that. It's not a dazzle, dazzle Hollywood romance.

"[Alexandra] is a cool, elegant woman, very quiet, very low-key. [Keanu] is a really great guy, too, but he's really lucky."

Keanu and Alexandra first collaborated in 2011 on his book 'Ode to Happiness', with the artist providing the illustrations, and reunited again to work on his 2016 book 'Shadows'.

The following year, the duo co-founded X Artists' Books, a publishing house that focuses on publishing "thoughtful, high-quality, artist-centred books that fit within and between genres".

It was first claimed last October their relationship had turned romantic.