Amy Winehouse's husband "ambushed" in prison

Amy Winehouse's incarcerated husband Blake Fielder-Civil has been beaten black and blue while in jail.

Blake -- who's on remand at London's Pentonville prison accused of assault and perverting the cause of justice -- received a beating from inmates who believed he was carrying heroin.

A source said: "Blake's been running scared ever since he set foot inside Pentonville—and now his luck has run out.

"He got ambushed by a few blokes who thought he had heroin on him.

"He's been put in solitary three times already for failing drug tests so they figured it was a fair bet he'd be carrying some—although he wasn't."

The source claims that Blake, 25, was lucky to escape the incident with just a black eye.

The source added to Britain's News of The World newspaper: "Because Blake is such a high-profile inmate, he's a natural target on the landings.

"There have been lots of threats and for a long time he just kept himself confined to his cell—he'll be staying there a lot more now."

Meanwhile, troubled Amy, 24, is set to fly to Malibu to check herself into rehab.

The 'Rehab' singer has reportedly booked in at the $10,000-a-week Promises clinic.

A source said:  "Amy knows she's on the fast track to ruin with the way her life's going. Her personal problems are starting to overshadow her phenomenal success.

"She's even been blasted by the United Nations for setting a bad example!

"With her husband Blake in choky, it's hardly a shock that she's hiding behind the crack cocaine and heroin. She's still a young woman living her life with the unique pressure of massive fame and she obviously can't handle it—just look at the self-harming.

"This is her chance to make a serious attempt at stopping the rot before it goes too far.

"No one wants her to end up the way of Janis Joplin."

The clinic has already treated high-profile stars like Britney Spears, Mel Gibson, Diana Ross, Christian Slater and Ben Affleck.