Rhys Ifans' Sienna fight

Jun 9, 2008, 10:10 GMT

10/18/2007 - Rhys Ifans - ... © Solarpix / PR Photos

Rhys Ifans has reportedly threatened to beat up the man he believes destroyed his relationship with Sienna Miller.

The 'Notting Hill' star - who was dumped by Sienna for being jealous of her ex-boyfriend and latest movie co-star Matthew Rhys - is devastated by the split and has warned he will attack Matthew if he finds out Sienna cheated on him.

He has also warned he will humiliate Sienna and Matthew at the upcoming world premiere of their film 'The Edge of Love' by turning up for a public showdown.

A source told Britain's The Sun newspaper: "He has taken this break-up really badly. He's spent the week drinking and texting Sienna, begging her to change her mind.

"His hurt has now turned to anger and he has said he will sort Matthew out when he sees him. He is raging.

"His last message to Sienna said he will ruin her big night at the premiere. She thinks he is serious."

The movie is due to have its first showing at the Edinburgh Film Festival on June 19.

Sienna, 26, is said to have dumped Rhys over the phone, citing their long-distance relationship as the reason.

Rhys, 39, is believed to have been upset over the amount of time she was spending with Matthew.

A source said: "Sienna broke the news at the weekend in a call from Prague. Things have been awkward for a while after she caught Rhys going through her text messages. She went mad and Rhys said he was looking for what he called 'incriminating evidence'."