The property near Spaghetti Junction has been acquired in an off-market, undisclosed deal from Manchester-headquartered Urban Splash and The Pears Group by European Property Investors Special Opportunities 3 (EPISO3).
The fund is advised by pan-European real estate investment manager Tristan Capital Partners.
Fort Dunlop is 375,000 sq ft and comprises mainly office accommodation, with tenants such as Birmingham Post and Mail, Regus and Capita, alongside a Travelodge hotel, ground floor retail units and 1,100 parking spaces.
The sale will be seen as another welcome boost to Urban Splash which secured a £135 million refinancing deal in April and last month returned to the black after racking up losses and debt totalling more than £200 million in recent years.
Tom Bloxham, chairman of Urban Splash which also redeveloped Birmingham's Rotunda, said: "We are very proud of the job we have done at Fort Dunlop.
"This is a project we've taken from an unloved wreck to a true icon of regeneration, which we've been incredibly pleased to have acquired, built, marketed, let and now sell.
"We believe that our work is now complete and are pleased to be passing it onto Tristan so we can concentrate on our exciting new development pipeline."
Peter Mather, managing director at Tristan Capital, added: "Its purchase reflects the attractive opportunities that we see for well-located grade A assets in the main regional cities of the UK and follows our investment in central Manchester in March."
Jonathan Rose, group managing director of Pears Property, said: "We are delighted with this deal.
"This sale of Fort Dunlop has allowed our JV with Urban Splash to repay a significant amount of debt at this very early stage."
Fort Dunlop was built in 1920 and was the main building of the former Dunlop Rubber factory area.
Its principal use was for the storage of tyres but it was derelict for two decades until its redevelopment by Urban Splash and it re-opened in 2006.
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