Sienna's surprise: Rhys plans to 'propose' for her birthday

Sienna Miller's burgeoning relationship with Rhys Ifans appears to be getting even more serious - the Welsh actor is planning to propose.

The Factory Girl actress celebrates her 26th birthday today and the Notting Hill star has planned a series of surprises for his girlfriend of five months.

Ifans has composed a poem in his native Welsh and has bought a selection of 10 gifts for Sienna, one which is rumoured to be an engagement ring.

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A friend of Rhys tells The Sun, "He's collected ten presents for Sienna of varying shapes, sizes and prices.

"They are all part of his plan for a romantic night in with a mountain of presents.

"Sienna is having a bit of an age crisis, feeling that she hasn't done enough with her life.

"So Rhys, whose philosophy is to live and enjoy every day, has penned a poem about their brilliant future together, all her achievements in life so far and always seizing the moment.

"He is keeping tight-lipped on a proposal but hinted to me that he has had a Welsh designer craft a special ring for her... which can only mean one thing."

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The couple have been dating since August this year and were 'outed' as a couple after they were photographed holidaying in Ibiza.

Despite being inseparable, the couple initially insisted they were "just friends" and Rhys was sleeping on Sienna's couch becuse his houseboat was leaky.

The couple took their relationship up a gear earlier this month when they fled to Mexico for a romantic holiday.

Sienna was famously engaged to Jude Law, who she met on the set of Alfie in late 2003.

After accepting Jude's proposal on Christmas Day 2004, the couple split up after the actor admitted to cheating on Sienna with his former children's nanny Daisy Wright.

Despite a reconciliation, Jude and Sienna finally split for good last year.