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Amy Winehouse's ex-husband, Blake Fielder-Civil, has apparently made good on his promise (read: threat) to reunite with her once he got out of court-ordered rehab.

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Britain's News of the World says the substance-susceptible exes, whose epically dysfunctional two-year union officially ended late last month, had a clandestine rendezvous over the weekend, which was believed to be their first meeting in more than a year.

The get-together allegedly culminated with the problem-beset singer, who returned to London in July after eight tequila-soaked months on the Caribbean island of St. Lucia, sneaking her jailbird ex-hubby through the window of her London home to avoid her two-man security detail, who were under orders to keep him away.

"They had a great night. Amy loved being in his company again," an insider tells the tab. "After everything they've been through, the pair both realize there's still something strong between them."

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And that something has Winehouse's father, Mitch, seeing red. According to the London Sun, the onetime cabbie rushed to Amy's house after being alerted to Blake's presence by her apparently ineffective minders.

Mitch, who is said to have heart and blood pressure issues, purportedly found them in bed together and warned his former son-in-law that he was going to "punch his lights out" as he gave him the heave-ho.

"Mitch hates the fact he's reappeared -- it's making him ill. It'll force him into an early grave," overdramatizes a source. "Blake begged Mitch not to hit him when he chucked him out. Mitch was absolutely furious, he still is. He can't believe Blake has wormed his way back into his daughter's life."

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Daddy Winehouse, who in a recent British documentary predicted that Amy and Blake "would kill each other if they got back together," believes a reconciliation is "the worst scenario for Amy," according to the insider.

"Just when she's starting to sort herself out, the man responsible for dragging her into the gutter is crawling back into her life," sighs the snitch. "Mitch is praying history doesn't repeat itself."