It seems unlikely that an interest in the history of microbiology would bring one to the roof garret of an 18th century church in Southwark.

St Thomas’s church, however, is the somewhat bizarre location of Europe’s oldest surviving operating theatre, providing visitors with a chilling glimpse of the days before anaesthesia and antiseptic surgery. In 1821 the church adjoined the end of the women’s block of St Thomas’s Hospital (which had been in Southwark since the 12th century), when it was decided that a new operating theatre for women would be built in the attic of the church. Until then, surgery had been performed on the ward. The attic was readily accessible from the hospital since it was already being used by the hospital apothecary for the storage and drying of medicinal herbs. Conversion to a modern operating theatre replaced part of the church roof with a large skylight and a tiered gallery was installed, allowing spectators to view operations. 

Surgery without anaesthesia almost defies imagination, though the novelist Fanny Burney gives a vivid picture of the ordeal in a harrowing account of a mastectomy she underwent in 1810. In such circumstances, speed was of the essence and virtuoso surgeons capable of performing an operation in minutes or less became celebrities – clearly doing rather more to merit celebrity status than appears the norm today. 
One such surgeon was Robert Liston. A Scot, Liston had studied and worked in Edinburgh, at the Royal Infirmary, but he was an opinionated and abrasive man who quarrelled with the authorities and was expelled from the Infirmary, heading south to England where he became Professor of Clinical Surgery at University College Hospital, a few miles from St Thomas’s.  
Liston was able to amputate a leg in as little as 30 seconds and would challenge his students to time him. Unlike many of his contemporaries, he would remove his frock coat, wear a clean apron and wash his hands before surgery and this was probably a factor in ensuring that 85% of his patients survived amputations, compared with 75% at nearby St Bart’s. His record, however, is not one of unalloyed success: in one amputation it is said that he severed the fingers of an unfortunate assistant holding the leg; the assistant and the patient both later died of infections, and a spectator succumbed to a heart attack brought on by his close proximity to the action, thereby achieving an unenviable 300% mortality rate in a single procedure.  
In 1846, Liston was one of the first surgeons in England to use ether as an anaesthetic. Unwilling or unable to change his approach, he still performed the amputation in 30 seconds and had to show the revived patient his severed leg to convince him that the operation had taken place. One of the students in his audience at University College that day was Joseph Lister, destined to achieve even greater fame as a pioneer of antiseptic surgery. 
Lister was born into a Quaker family at Upton House in West Ham. His father was a wine merchant by trade but was elected a Fellow of the Royal Society for his work on the optics of microscope design. After studying medicine in London, where he published papers on gangrene and the use of the microscope in medicine, Lister went on to become Professor of Surgery at the University of Glasgow. It was here that he was introduced to the work of Pasteur by Thomas Anderson, a professor of chemistry. Lister immediately saw the impact this would have on his own research and sought ways of destroying the organisms responsible for post-operative infection. For this, he adopted carbolic acid (phenol), a coal tar distillation product with known antiseptic properties already used in the disinfection of sewage. In an 1867 paper, Lister described treatment of the wounds in compound fractures with his new antiseptic methods and lauded ‘the flood of light’ Pasteur’s work had shed upon the problem. He continued to promote and modify his antiseptic technique, later abandoning, for instance, his famous carbolic spray, having been convinced that the principal sources of infection were the surgeon, the patient’s skin and the dressings, and that the adverse effects of the caustic spray on breathing and the eyes outweighed any advantage it offered.  
For his pioneering role in developing antiseptic surgery Lister was deluged with honours ranging from a baronetcy and the Order of Merit to a proprietary mouthwash bearing his name. Perhaps the most novel tribute is a small flask of Lister’s urine (passed circa 1868) on permanent display in the Hunterian Museum in Glasgow – clear and uninfected to this day, though a decidedly unhealthy-looking brown colour. 
The St Thomas’s operating theatre saw the introduction of anaesthesia but closed before the advent of antisepsis when, in 1862, the nearby railway into London Bridge was allowed to extend its lines across the Thames to Charing Cross and Cannon Street. St Thomas’s had to move, eventually to its present site 2 miles upstream in Lambeth, opposite the Palace of Westminster.  
At St Thomas’s church, however, with the repurposing and demolition of surrounding buildings, the operating theatre in the loft was largely forgotten. It was ‘rediscovered’ in 1956 when Raymond Russell, researching the history of the hospital, decided to investigate the church’s attic. His only access was by placing a ladder up to an opening 15 feet above the floor of a second-floor chamber in the tower. Climbing into the dark void (the glass in the skylight had been replaced with slates) he found that though some features had been removed, much remained in place. Sufficient, in fact, for the theatre to be expertly reconstructed, enabling those prepared (and able) to climb the 52 steps the chance to visit a poignant reminder of how the study of microbiology has contributed to human wellbeing