By THOMAS WHITAKER and TRACEY KANDOHLA, THE SUN

Movie hunk Jude Law and wife Sadie Frost are living under separate roofs less than half a mile apart.

Sadie — who has been suffering post-natal depression — is staying in the couple’s new £2million house with their three children. But Jude is at their old £1million house just three roads away.

A pal of the couple said last night: “This speaks volumes about the state of their marriage. Publicly they are saying their marriage is rock solid. But behind the scenes there are serious problems which are appearing irretrievable.

“Sadie is going through the worst spell in her life. She has been in hospital for days and is desperately unhappy.”

The couple’s old house in Primrose Hill, North London, is stripped of furniture and so empty that Jude, 30, had to pop out yesterday for a takeaway coffee.

A neighbour said: “There isn’t even a kettle in the house. We thought we wouldn’t see Jude back here again.”

Road to Perdition star Jude and Sadie, 37, have tried to put on a public show of unity. On Tuesday morning they grinned for photos with the children.

But within two hours Jude left. He spent the night at their old house and returned to Sadie’s at 7am yesterday.

Jude — who only arrived back in Britain from America four days ago — left again three hours later without comment.

He has angrily denied rumours he cheated on Sadie with film star Nicole Kidman, 35, his co-star in new film Cold Mountain.

Asked about their marriage problems yesterday, Dracula star Sadie insisted: “At the moment they are fine.”

She has told friends she is not giving Jude up “without a fight.” But Jude is alleged to have told her their five-year marriage is over.

A pal said: “They need some space. Things have been very heated. It was better to spend the night apart.”

Sadie has been comforted by phone calls from film star pal Gwyneth Paltrow. The Sun told last week how Sadie needed treatment after marking her arms in “a cry for help”.

Sadie’s brother Toby Vaughan, 21, of Manchester said: “I really hope they can work things out. They both think the world of the kids and that might keep them together.”

She and Jude have a five-month-old son Rudy, daughter Iris, two, and seven-year-old son Rafferty. Sadie also has a son Finlay, 12, by her first hubby, Spandau Ballet pop star Gary Kemp.