LONDON - London City skyscraper Tower 42 is up for sale with a 300 million pounds ($461 million) pricetag as owners BlackRock and Hermes seek to profit from spiralling demand in the UK's stock-starved property market.

After 12 years of ownership, the fund manager and pension fund said on Tuesday they wanted to sell the freehold title of the 600-foot landmark office property, which is 95 percent let and the tallest occupied building in the City of London.

With significant global demand now focused upon central London offices driven by expectation of future returns, combined with a dearth of trophy assets on the market and weak sterling, the partners believe that the timing is right to market the asset, Marcus Sperber, managing director at BlackRock, said.

In addition to the 324,000 square foot multi-let skyscraper, the Tower 42 estate includes five other commercial buildings on a 2.2 acre freehold site.

Offers in this range would reflect a net initial yield of about 6.5 percent and a capital value of about 630 pounds per square foot, the partners said.

The planned sale is seen by some as evidence for Britain's rapid real estate comeback but some experts fear the recovery may seize this year as banks begin a long-awaited programme of distressed asset sales that may trigger fresh price falls.

Average UK commercial property values are expected to decline by 0.6 percent in 2011, compared with predictions of a 2.2 percent annual rise just three months ago, a February survey conducted by the Investment Property Forum (IPF) showed.

Despite the uncertain outlook, Hermes' director Chris Darroch said the opportunity was a very interesting proposition for a global investor keen to make their mark on the City landscape.

Advisor Jones Lang LaSalle is marketing the property. Hermes is owned by British Telecom's pension fund. (Reporting by Sinead Cruise; Editing by Andrew Macdonald) ($1=.6511 Pound) (See for the global service for real estate professionals from Reuters)