After working on the fringe in London (Finborough, the Old Red Lion) Schlesinger joined Compass Theatre Company and toured for two years, mainly Shakespeare, throughout the country and abroad.
Helen played Viola in Twelfth Night and Portia in The Merchant of Venice for the Royal Shakespeare Company in Stratford and the Barbican.
At the Royal Court productions, appearances include Wild East by April de Angelis and The Stone by Marius Von Mayenburg and Fireface at the Young Vic by the latter playwright.
Helen played Elizabeth Proctor in The Crucible for the RSC (which transferred from Stratford to the Gielgud Theatre) for which she won Best Supporting Actress at the Whatsonstage Awards.
At the Donmar Warehouse, Helen played Sicinius in their recent production of Coriolanus and Elizabeth in Alexi Kaye Campbell's Bracken Moor at the Tricycle Theatre.