Derwent London, which rents out offices in the capital, remained stuck in the red during 2009, but a "substantial recovery" in central London property values during the second half of the year has continued into 2010.The company said rents within its central London portfolio have virtually stabilised and rental growth is on the cards for the first time since early 2008.A reported loss before tax of £34.9m was much less than the £606.5m posted the year before as the revaluation of its property portfolio cost its £81.1m compared with £602.1m in 2008.Adjusted net asset value per share hit 1,168p at the year-end thanks to an 18% improvement in the second half, up from 993p at the end of June. That limited the full-year decline to 4.7%, down from 1,226p in December 2008.There was a portfolio revaluation surplus of £177.8m in the second half, with a 9.8% valuation increase since the half-year partially offsetting the 12.3% decline in the first half, resulting in an annual valuation reduction of 3.3%."Following a successful performance in 2009, the group has made a strong start to 2010," said chief executive John Burns. "I am encouraged by the continued demand for our contemporary space as demonstrated again today by the lettings at the Charlotte Building." "As the recovery of the central London economy appears to be gathering momentum, we continue to implement Derwent's distinctive brand of regeneration and, where possible, are accelerating schemes." The company said Wednesday it has attracted two new lettings at its new flagship Charlotte Building in Gresse Street, London worth a total of £900,000 a year.Shoe designers Converse, owned by Nike, has taken a 10½-year lease at £0.65m per annum, while packaging design specialist Brandopus will pay rent of £0.22m each year on a 10 year lease. Six out of the seven floors are now let."Although only completed in October last year, the vast majority of the space is now let, reflecting the continued demand from tenants for our high quality yet affordable central London space," said Burns.The final dividend rise 15% to 18.85p a share, making a total payout of 27p, 10% on the previous year.