Lehman in its complaint alleged that JP Morgan misused its position as clearing agent then, and accelerated its failure by seeking $8.6bn of collateral during the financial crisis. This left Lehman with no other option but to declare bankruptcy over the weekend, rather than having liquidity to open for business on September 18, 2008, and begin an organised withdrawal from derivatives and other contracts.

Now, Lehman is seeking return of that $8.6bn from JP Morgan, plus billions more as compensation for lost value.

Lehman’s lawyers said: “The effect of JPMorgan’s actions, taken with the benefit of unparalleled inside knowledge, was devastating.”

A JPMorgan spokesman termed the Lehman lawsuit ‘ill-conceived’ and said Lehman had nobody but itself and its investment in subprime mortgages to blame for its downfall.