AllianceBernstein’s chief operating officer David Steyn, who played a leading role in putting the US-based asset manager on the map in the UK a decade ago, is stepping down.

Steyn, a partner at AllianceBernstein and chief executive of its London subsidiary, will leave on January 3. He joined the firm in 1999 as founding co-chief executive of the London arm of Sanford C Bernstein, the manager's sellside research unit.