Alexander Henderson, Singapore-based managing director at the eponymous Henderson Global Investors, says the firm’s acquisition of Gartmore Group in the United Kingdom could make it the biggest manager of Japanese long/short equity strategies.

He is unable to say exactly how big the combined Japan investment team in Tokyo will be post-merger, because the details are still being negotiated with shareholders, not to mention awaiting regulatory approval from Japan’s Financial Services Agency.

The Gartmore acquisition is more about business in Europe and follows Henderson’s purchase of UK fund manager New Star in 2009. The combined entity would give Henderson a total AUM of £78.1 billion ($124.2 billion), up from Henderson’s £61.6 billion today.

A big focus of the acquisition is to increase Henderson’s portfolio of absolute-return strategies, to over £6 billion. Many of these involve Tokyo teams.

Henderson already runs all-cap equity long/short portfolios in Japan, managing $450 million.

Around 8% of Gartmore’s £16.5 billion, or £1.3 billion ($2.1 billion), comes from its own large-cap long/short Japan equities team. Currently Gartmore has two portfolio managers and three analysts in Tokyo.

Alex Henderson declined to comment on how the teams will be structured, but calls the two desks complementary, and the firm says John Stewart, a Japan long/short manager at Gartmore, has already confirmed he will join Henderson.

Both Gartmore and Henderson sell absolute-return strategies to institutional and retail investors.

Once the integration of Gartmore is completed by late spring, Alex Henderson says Japan, Australia and China will be important markets for adding resources and beefing up the firm’s offering in listed assets, real estate and private equity.

“The group will support a sensible acquisition, alliance or joint-venture in those markets,” Alex Henderson says.