The Atrium in Uxbridge is a 138,000 square feet (sq ft) office block let to companies including American oil and gas firm Anadarko and accountants PwC.
Blackrock said the deal offers a net initial yield of 5.7 per cent and has an estimated capital value of £405 per sq ft.
“Uxbridge is a historically stable market, particularly within the office sector, and as such attracts premier tenants,” Justin Brown, portfolio manager, said.
“The Atrium is one of the best multi-let office properties in the south east.
“It offers attributes that are difficult to replicate in modern buildings, providing atrium space, strong natural light and car parking which are all attractive characteristics to long term premier tenants,” he added.