Showbiz
Photorazzi / Chris Hatcher
The thespians have previously denied that they are in a relationship, insisting that they are just good friends.
However, Miller was seen having an intimate embrace with the Notting Hill actor on West London Street at the weekend, according to the paparazzi.
An onlooker told The Sun: "There's no way they are just mates. They looked like a couple very much in love.
"They were holding hands as they walked the dogs and then stopped to share a lingering kiss. Sienna couldn't stop smiling."
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