Kiln plc estimates its losses due to last week's terrorist attacks in the US at $45m (£30.6m).
The firm is one of the largest managing agencies in the Lloyd's insurance market with a capacity of nearly £350m for the 2001 year of account. R J Kiln manages four syndicates and Kiln South Africa.
Its board stressed the figures were only an initial estimate of the net loss to its managed syndicates, after taking into account syndicate reinsurances.
Syndicate 510 is expected to lose £11m for the 2000 year of account and £16m for the 2001 year of account. Syndicate 557 is expected to lose £18m for 2001.
The Kiln Underwriting share of the figures equates to 16p per Kiln plc share.
The company said in a statement that its estimates were within ranges previously calculated for realistic disaster scenarios and did not include any provision for reinsurance failure or profits from other trading.
The losses will be included in the results for the second half of this year.
