The bankruptcy estate of Lehman Brothers Holdings Inc. accused some former executives of working with Barclays PLC to give the U.K. bank a "windfall" of at least $8.2 billion when it bought Lehman's broker-dealer business during a frantic sale last fall.

The Lehman estate, which represents the interests of the firm's creditors, accused its own former executives of helping move billions of dollars to the U.K. bank, in part to curry favor with their prospective employer.

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