LONDON — Michael Attenborough, a.d. of the Almeida Theater, will step down from his post in spring 2013.Attenborough has been at the helm of the 330-seat North London venue for 11 years. During his tenure he has presented 32 U.K. and world premieres including plays by U.S. dramatists Lynn Nottage (“Ruined”), Gina Gionfriddo (“Becky Shaw”), Stephen Adly Guirgis (“The Last days of Judas Iscariot”), Edward Albee, David Mamet, Sam Shepard and Theodore Ward. Four productions have transferred to the West End and one show, “Festen,” also had a Broadway run in 2006. The theater’s current production is “King Lear,” helmed by Attenborough and starring Jonathan Pryce. Despite a recent cut in in its Arts Council England grant — the theater took an unexpectedly high 39% hit — the company remains one of the capital’s leading not-for-profits. Competish for the a.d. slot is expected to be fierce.