Derwent said its full-year net rental income increased 5.8% to £128.7m, as the real estate investment group achieved higher margins on lettings.Pre-tax profit rose 7.8% to £62.3m in 2014, while earnings per share grew 6% to 57.08p. Net asset value climbed 28.4% to 2,908p. The strong performance came off the back of £9.2m of new lettings and a 9% rise in underlying estimated rental values.The group raised its full-year dividend 8.6% to 39.65p per share.Looking ahead, the group hopes to benefit from post year-end activity including £5.9m of rent secured from new lettings in 2015 to date and the acquisition of London's 20 Farringdon Road EC1 through a £115.3m property swap.Derwent has begun the 105,000 sq ft development at The Copyright Building in west London west and applied for planning permission to develop a 110,000 sq ft hotel and office scheme in the south east of the city.Chief executive John Burns said: "Derwent London is well positioned to benefit from the numerous creative opportunities within the portfolio. Overall we see scant evidence so far of a commercial property slowdown in London and we expect to see rental growth at least maintained at 6-8% across the portfolio, and investment yields to remain firm in 2015."We remain very confident in our business and our markets, and over the next few years look forward to delivering a substantial phased development programme to meet occupier demand."