Lloyd's of London has announced it is bringing legal action against two brokers after accusing them of failing to protect its assets.
Aon and Benfield have been informed they will face action in a bid to force payment of £325 million.
Lloyd's says the funds equate to the losses it suffered when six insurers won a legal battle against the London firm.
Costs incurred despite its policy with Aon and Benfield now form the basis of the case.
Lloyd's was left with a £500 million bill after losing the case, with the policy providing just £152 million.
Now it is planning on retrieving the costs from Aon and Benfield, saying it has informed the duo of its intention, although it has not yet made a formal application to the courts.
The case may not be heard for a further 18 months, although Benfield has said it will "defend any action vigorously".