Robbie WilliamsRobbie Williams has flown back to the UK to be with his poorly mum.

It's believed the star jetted back from his home in LA on Saturday to be with Jan, who underwent heart surgery yesterday.

According to The Sun, the pop star was at his mum's bedside at a private hospital in Cheshire before she went in for bypass surgery.

The paper quotes a source as saying that Jan is in a "critical but stable" condition, as of last night.

Robbie Williams and mum Jan"She will almost certainly spend Christmas Day in hospital, but if all goes well she might be discharged by New Year," the source said.

"Robbie is desperate to make sure everything goes exactly to plan."

Robbie has always been very vocal about his love for Jan - believed to be the inspiration behind Angels.

She brought him and his sister up as a single mum and Robbie has said in the past:

"I can't wish for anything more than I've got with my mum and sister. What I've got is fantastic."