Lloyd’s of London plans to sue brokers Aon Corporation and Benfield Group for £325 million ($766.2 million) for payment of a claim related to the September 11 2001 terrorist attacks.

Aon and Benfield were responsible for arranging insurers for a policy that Lloyd’s bought for itself in 1999, but was left out of pocket when the policy’s six insurers refused to pay up to £500 million ($1178.9 million) in claims that Lloyd’s presented.

Lloyd’s eventually settled the dispute in March last year, receiving £152 million ($358.5 million) from the insurers. Lloyd’s 2004 profits took a £276 million ($650.9 million) dive when it was forced to write off the extra payments it originally anticipated receiving under the policy.

It is likely to take up to 18 months for the case to come to court.