AM Best has affirmed the ratings of two Lloyd's syndicates managed by Bermuda re/insurer's Ariel Re's London-based subsidiary, Atrium Underwriters Ltd.

Syndicates 609 and 507 (United Kingdom), both maintained the Best's Syndicate Rating of A (Excellent) and issuer credit rating of "a+".

Syndicate 609's capacity will rise to £275 million for the 2010 year of account from $200 million last year, primarily reflecting the weakening of sterling against the US dollar, while Syndicate 570's capacity will rise to £145 million next year from £125 million this year.

Rate strengthening for the syndicates' catastrophe-exposed business is expected to support an improvement in their combined ratio, or percentage of premium dollars spent on claims and expenses, in 2009

Syndicate 609's combined ratio was 104 percent in 2008, a result which was impacted by hurricanes Ike and Gustav, while 507's was 99 percent.

Best added thata solid net investment yield is anticipated, albeit lower than the four percent achieved in 2008.