Just days ago, Rhys Ifans was cuddling up to a Sienna Miller lookalike on the shores of Ibiza.

But after returning to London this week, the mystery blonde appeared to have been substituted for a famous blonde... Rod Stewart's daughter Kimberly.

Rhys and Kimberly were first spotted together last month, after they were seen partying together and the actor spent the night at the socialite's London home.

Home time: Rhys Ifans and Kimberly Stewart share a cab home together after their epic pub crawl through Soho

The couple spent the whole day together yesterday on an epic pub crawl through Soho.

After starting the afternoon drinking at a pub, the pair moved to the Groucho Club, before ending the evening at trendy new club Bungalow 8.

But while their relationship looks increasingly like it could be more than friends, the pair took great pains not to be photographed in an embrace.

Hot date: Kimberly Stewart changed into a colourful mini-dress halfway through her date with dishevelled Rhys

As they hailed a cab home at 2.30am this morning, the couple sat far apart from each other and attempted to cover their faces from the crowd of paparazzi outside.

Despite starting off the day in a jeans and cardigan combo, at some point in the night, Kimberly decided to glam up proceedings and briefly popped home to change into a sequinned argyle mini-dress.

Rhys and Kimberly have refused to discuss the nature of their relationship, but have been spending increasing amounts of time together in recent weeks.

Smoking hot couple: Kimberly and Rhys enjoy a cigarette break with friends outside one of the many pubs they visited yesterday

The Notting Hill actor, 40, was left heartbroken when Sienna called time on their nine month relationship in May - just weeks before her high-profile affair with millionaire oil heir Balthazar Getty was made public.

It's the second time Kimberly has been linked with one of Sienna Miller's exes.

She was photographed in a passionate clinch with the Factory Girl star's former fiancé Jude Law in an Essex nightclub just three months ago.

Who's that girl? Rhys was spotted with a blonde Sienna Miller lookalike in Ibiza last week