LONDON (Bloomberg) - British Land Company, the UK's largest real estate investment trust by assets, leased 39 percent of a tower it's building in London's main financial district to law firm Reed Smith Richards Butler LLP.

And in the same part of London it is also leasing out space to Bermuda-based insurer Axis Capital Holdings.

Reed Smith will occupy 11 floors of the 540-foot Broadgate Tower with space of 155,000 square feet, British Land said. It is the first letting for a building that is due to be completed next year.

British Land decided in November 2005 to construct the tower and an adjacent building before it had found tenants. This is the first time an office tower has been built on a speculative basis in the City of London district, according to British Land. The company has leased 70 percent of the available space in the two developments.

Reed Smith Richards Butler will initially pay an average rent of £58 ($117) a square foot for the premises, or about £9m ($18.2m) a year. London's offices command the world's highest rents.

Reed Smith Richards Butler is the UK arm of Pittsburgh- based Reed Smith, a firm with more than 1,500 lawyers in 21 offices across the US, Europe and the Middle East.

In a separate statement, London-based British Land said it leased 57,000 square feet of space in the same part of the UK capital to Sempra Energy, a San Diego-based energy services company, and Bermuda-based insurer Axis Capital Holdings.

British Land shares have fallen 19 percent in the past six months.