Grosvenor Group Ltd., the property company owned by the family trust of the Duke of Westminster, reported a narrower loss for 2009 as the slide in the value of its assets slowed.

The net loss, excluding minority interests, shrank to £190.6 million from £456.9 million a year earlier, London-based Grosvenor said today on its Web site. Net asset value fell 10% to £2.54 billion.

The value of the properties owned or managed by Grosvenor fell 18% to £10.2 billion. Grosvenor sold buildings, shed 49 staff and slowed development projects, increasing the amount of cash or loans available by 84% to £964 million.

“This was not a year for bold initiatives,” said Mark Preston, 42, Grosvenor’s chief executive officer, in the annual report published today. Instead, it was one “of cautious ‘good housekeeping,’ which positions us well for the future.”

Profit from rental income, trading and development, which excludes the changes in values of Grosvenor’s investment properties, totaled £62.2 million compared with a loss of £76.7 million a year earlier.

Over time Preston intends to step up investments in Asia and London, while strengthening Grosvenor’s fund management business.

“We do not expect 2010 to be an easy year,” Preston said. Grosvenor will only start investing “when we are confident that the timing is right.”

Australia, where Grosvenor has invested for 42 years, provides a short-term opportunity after it weathered the financial crisis thanks to trade links with China and a growing population, he said.

In China, Grosvenor has been “taking our chips off the table as a tactical move because of the rapid ramp-up in pricing,” Preston said. “It won’t be long before we reinvest.”

Preston said debt concerns in the U.S. real estate market have prompted the company to concentrate on longer-term development projects. In the U.K., Grosvenor’s focus on London should protect it from the country’s uncertain economic outlook, he said.

The company’s asset management arm has plans to start four funds, the most advanced of which will invest £400 million in London offices. Other possible funds may invest in office developments in Washington, real estate in Tokyo and European shopping centers.

The Grosvenor family’s ancestral London land holdings are in Mayfair and Belgravia, among the world’s most expensive locations in which to lease an office or a home. The company diversified outside the U.K. and Ireland to own or manage assets such as a warehouse distribution center in Vancouver, part of the Paris flea market and luxury condominiums in Shanghai.

The Duke of Westminster is Britain’s wealthiest individual. He was ranked 45th in Forbes Magazine’s March list of the world’s wealthiest people, worth $12 billion.

The Duke, Gerald Grosvenor, isn’t the wealthiest individual residing in the U.K. That title goes to Lakshmi Mittal, president and CEO of ArcelorMittal, the world’s largest steelmaker.