Hiscox is in confident mood after boosting premium income by 31.7% in the first nine months of 2009, giving the specialist insurer "good reasons to be optimistic".The third-largest underwriter at Lloyd's of London reported gross written premiums up to £1.2bn for the year so far versus £920.1m during the same period in 2008. Year-on-year growth at constant exchange rates was 10.5%.Hiscox London Market, which underwrites mainly internationally traded business in the London Market, posted a 27.3% rise in gross written premiums to £575.7m, thanks to favourable exchange rates. Without that help they were down 0.1%.Meanwhile, the established retail business in the UK kept providing "steady growth", with gross written premiums up 16.5% to £228.7m, driven mainly by Hiscox's commercial lines business. "With strong investment returns and overall growth, we have good reasons to be optimistic," it said.The investment yield to 30 September 2009 was +6.5% following a strong third quarter return of +3%. Non-government bonds and equities have continued to perform well. Chairman Robert Hiscox said the company is in "good health". "We have continued to benefit from solid investment decisions and have maintained growth in our most profitable underwriting lines," Hiscox said. "Rates are stable and still very healthy in most areas, particularly reinsurance which accounts for over a third of our business. Our mix of business is designed for these market conditions."