Amy Winehouse's hubby Blake Fielder-Civil's mystery girlfriend, who he affectionately calls "Darling Tickle", is a 25-year-old office receptionist Sarah Thomas, it has emerged.

Fielder-Civil is smitten by Thomas, who has been secretly visiting him in Pentonville Prison, while Winehouse has been missing.

Thomas, who Blake is planning to have a future with, is also helping him get clean of drugs while he's inside.

"Just say the word and I'll dump Amy. I love you more than I could ever love my wife. You're all that matters to me," News of the World quoted him as saying.

He is so besotted with her that he even has told his mum Georgette about his feelings for her.

"Unlike Amy, Sarah always turns up to visit me. She's always there for me," he said.

"She knew me before I got addicted to drugs and told me how much she hated the way I changed when I got stoned with Amy. She's helped me get clean of drugs in prison. Now I feel I'm in control and I appreciate what an absolute s*** I've been when I was stoned.

"I'm determined to stay clean," he added.

Blake, who heard the story of Winehouse seeing her manager's assistant Alex Haines, bragged to his pals that she will have to pay him a seven-figure sum if they split.

He is set to demand at least 3million to 250,000 pounds a month for their yearlong marriage.

Blake was dismayed when he heard that Winehouse had been cheating on him and he has been pouring his heart out about the betrayal to loyal Sarah, who he's known for five years and has been his rock since he was put behind bars on remand.

He has been sending love letters to Thomas from prison, in which he addresses her with pet names like "Darling Tickle", "Ma Cherie" and "Baby".

"He's crazy about her. They're really touching letters-the sort any wife would be horrified to read," a friend of Sarah's said.

"Sarah has really taken the place of Amy in his heart. She's always there for him whereas it's a real hammer blow when Amy doesn't turn up on big occasions like his birthday," the friend added.

Blake's family on the other hand are delighted that he's moving away from the wayward Rehab singer.

"I've told him he should divorce Amy now and start a new life with Sarah. She's his best buddy and has been extremely supportive," his 45-year-old mum said on May 10.

"Amy's a mess. I've told him if he goes back to her she will lead him to an early grave," she had added.