John Horseman, one of the most well-regarded hedge fund managers in London, is throwing in the towel amidst big losses this year.

Horseman told investors Wednesday that he was giving up management of his two hedge funds “for personal reasons and also because of how I perceive the investment environment.” His flagship Horseman Global Fund, which will also lose assistant manager Mark Driver, will be taken over by Russell Clark and John Paul-Burke. Horseman’s Emerging Market Opportunities fund will be liquidated.

Horseman said he had planned to stick around for another few years before retiring, but his funds’ struggles seem to have changed his mind. The $3.6 billion Global Fund—which enjoyed huge returns last year while most hedge funds suffered double-digit losses—is down about 23% this year, when the average hedge fund is up almost 20%.

“There will be those who might think that a poor year is unduly influencing my decision, and it is probably true that if the fund had had a better year, I might have been tempted to continue for a while longer,” Horseman wrote. “But with a time frame of three to four years at most, I feel now is the most appropriate time to make way for others.”

Horseman and Driver will remain with the firm, although not in a day-to-day management role. Horseman will keep his controlling stake in the firm and will remain on its board of directors.

Clark takes over as manager of the Global Fund on Jan. 1.