Catlin Group has said pretax profit for the year to Dec 31 came in at $521m.
No comparable figures for the previous year are available, as the results are the first to include a contribution from Wellington.
When the Wellington acquisition is excluded, Catlin had a pretax profit of $275m, up sharply from $28m a year earlier.
The improvement partly reflects lower insured losses, which fell 21% to $681.5m from $865.3m.
The combined group had gross written premiums of $2.72bn, with Catlin itself contributing $1.6bn, up from $1.4bn in 2005.
The combined ratio stood at 87.3%. The combined ratio for Catlin alone fell to 88.2% from 103.2%.
"Given the advantages that the Wellington acquisition has provided to Catlin, the market environment, our experience to date in 2007, and the prospects of embedded and organic growth, I believe Catlin's prospects in 2007 and beyond are excellent," said Stephen Catlin, the insurer's chief executive.
The insurer added that it was looking for cost synergies of at least $70m from the takeover of rival Wellington Underwriting, which the company said was 'ahead' of original expectations.
