Chaucer is set to reduce the capacity of Lloyd's Syndicate 1084 by around 10% next year.
The move will see the syndicate's capacity drop by about £40m. Syndicate 1084 writes aviation, marine, motor, property and specialist lines.
AM Best recently assigned Syndicate 1084 an A (excellent) financial strength rating, with a stable outlook.
Chaucer will also boost the capacity of Syndicate 1176 by around 20% in 2005.
The increase will raise the capacity of the syndicate, which writes nuclear risks, from £15m to £18m.
Chaucer said last week that its 2004 year of account continued to develop positively as it announced its updated forecasts for its Lloyd's syndicates.
Chaucer said gross written premiums for the 2004 year of account were ahead of those recorded for the same point in 2003, with pricing remaining strong overall.
Gross written premiums to the end of June 2004, net of brokerage, were £243.4m, up 15% on the previous year.