It is possible that the Herb Garret existed in the attic of St Thomas’s Church as early as 1703. It was used as a place to store, dry and cure herbs prior to their use in medicines. In 1822 the governors of St Thomas’s Hospital decided to convert part of the Garret into an operating theatre for women. This is not as strange as it may first sound as a block which adjoined St Thomas’s Church included Dorcas Ward, where prior to 1822 any female surgery had been carried out on the ward as no theatre facilities existed close by.
In 1862, St Thomas’s Hospital relocated to Lambeth, the operating theatre was closed down and was almost forgotten for about the hundred years. In 1956 Raymond Russell, researching the history of St Thomas’s, decided to investigate the church attic to see what was there and found the operating theatre almost intact. Following restoration, it was open to the public as a museum in 1962.
For further details: http://oldoperatingtheatre.com/