Westminster Council has said that the collapse of the ceiling of the Apollo Theatre in Shaftesbury Avenue last December was caused by the deterioration of century-old cloth and plaster ties holding up timber frames.
The incident during the Curious Incident of the Dog at Night Time injured 80 members of the audience when 10 square yards of plaster plummeted on to the stalls below, and forced the closure of the grade II-listed theatre.
The ties, made of hessian and plaster of Paris, were used to lash together timber frames to support the suspended ceiling and had been in place since the theatre opened in 1901.
The Apollo will re-open this week for the first time since December 19.
More top news
Goals from Charlie Austin, Dusan Tadic and James Ward-Prowse consigned Slaven Bilic's men to their fourth straight Premier League loss.
A bizarre protest against BP sponsorship at the British Museum used theatre, sea shanties and 'mermaids' to 'summon a Kraken'.
Two men have been jailed for robbing a man aged 79 as he was washing his car.