Real estate is the worst-performing sector Thursday after British Land said its net asset value (NAV) per share slumped 64% last year, while its property portfolio lost almost two-thirds in value.The group's portfolio valuation is down by 28.2% and its NAV per share dropped to 398p. The portfolio includes the prestigious Broadgate complex in London.Meanwhile, £3.24bn of markdowns led to a widened full-year net loss of £3.88bn compared with a loss of £1.56bn last time. Underlying pre-tax profits came to £268m.Today's fall comes the day after real estate stocks were lifted by news that London's West End-focused Shaftesbury has joined the rush of property groups raising cash with a fully underwritten rights issue to raise £149.1m net.Investors have failed to warm to results from Cable and Wireless and the firm is leading the fixed line telecommunications sector lower.Revenue grew by 16% to £3.6bn, slightly less than forecast. Profit before tax for the 12 months ended 31 March rose to £422m from £308m a year ago, although exceptional items of £189m mean the total figure was down to £233m from £267m.Top performing sectors so far todayPharmaceuticals & Biotechnology 7,496.13 +0.41%Bottom performing sectors so far todayReal Estate 1,552.38 -4.73%Industrial Metals 3,733.23 -4.04%Fixed Line Telecommunications 1,442.99 -3.99%Banks 3,948.92 -3.96%Mining 14,081.94 -3.94%