The venue reopened on 26 March 2014, with an adaptation of "Let the Right One In" produced by the National Theatre of Scotland. The owners were able to reopen the theatre by sealing the fourth level and balcony with a temporary floor, which allowed investigators to continue their work in determining the cause of the collapse. That month Westminster City Council issued a notice to other historic theatres saying that the ceiling collapse appeared to have been caused by the gradual deterioration of Hessian wadding mixed into plaster of Paris to form the ties lashing timbers together, which had probably been in place since the theatre was built.