UPDATE 1-Advent Capital swings to Q1 profit; upbeat on '09

* Q1 pretax profit 1.9 mln stg vs loss of 5.5 mln stg

* Says Q1 results reflect benign claims environment

* Shares up 3.6 pct (Adds details)

April 28 (Reuters) - Insurer Advent Capital (Holdings) Plc (ADV.L) swung to a first-quarter pretax profit helped by higher gross premiums and a "benign claims environment" and said it expected market conditions to improve in 2009.

For the quarter ended March 31, the Lloyd's of London [LOL.UL] insurer posted a pretax profit of 1.9 million pounds ($2.8 million) compared with a loss of 5.5 million pounds a year earlier.

It said gross premiums written in the quarter, excluding the reinsurance to close premiums, increased 40.8 percent to 87.3 million pounds, partially reflecting the strength of the U.S. dollar, which rose 28 percent in 2008. "We believe that market conditions should continue to improve during 2009 as reinsurers and insurers alike seek to achieve better underwriting returns given low investment returns and reduced capacity," the company said in a statement.

The company also said its long-term debt, maturing in 2026 and 2035 was not subject to refinancing risk.

Advent Capital shares were up 3.6 percent at 145 pence at 0758 GMT on the London Stock Exchange. ($1=.6820 Pound) (Reporting by Austin Lobo in Bangalore; Editing by Tresa Sherin)