The activist hedge fund that suffered a disappointing defeat after a fierce battle with GAM, a $130bn investment manager, in April has become one of the best performers of 2017.

RBR Capital Advisors, which called for significant job cuts at the multibillion-dollar asset manager and wanted to axe its chief executive, gained 9.8% in May, pushing returns up to almost 16% for the year to May 31, according to widely-followed performance data compiled by HSBC.