In 1831 Panizzi was appointed to the post of "Extra-Assistant-Keeper" at the
British Museum Library over the objections of some who did not wish the post to be filled by someone not of the Church of England. For his extraordinary services as a librarian, in 1869 he was
knighted by
Queen Victoria, becoming a Knight Commander of the
Order of the Bath. The British Museum library was the
national library of the United Kingdom in all but name. During Panizzi's tenure as Keeper of Printed Books its holdings increased from 235,000 to 540,000 volumes, making it the largest library in the world at the time. Its famous circular
Reading Room was designed and built by architect
Sydney Smirke from a sketch drawn by Panizzi. The new reading room opened in 1857. The British Museum library formed the bulk of what became the
British Library in 1973 and the "Round" Reading Room was in use until 1997 when the Library moved to its current site at
St Pancras. During his tenure at the Library, Panizzi was embroiled in many controversies. Notably
Frederic Madden, Keeper of Manuscripts, opposed the appointment of Panizzi. Panizzi's appointment as Keeper of Printed Books was met with criticism due to Panizzi's Italian origin: some felt an Englishman should be in charge of the national institution. Other sources state it was because he had been "seen in the streets of London selling white mice." Panizzi also had a long-term dispute with historian
Thomas Carlyle. While Carlyle worked on his
history of the French Revolution, he had complained in a magazine article that "a certain sub-librarian" had not been very helpful to him, restricting access to uncatalogued documents held by the British Museum. Panizzi never forgot the slight and when Carlyle, now working on the biography of
Cromwell, requested the use of a private room at the library for his researches, the request was denied. Despite high-level complaints, Carlyle lost the argument; and he and his supporters opened their own independent subscription library, the
London Library. In 1835–1836 Panizzi recognised that the new Select Committee of the House of Commons on the British Museum would be seeking accountability as to procedures. To prepare with comparative data he visited the main libraries of Western Europe, Italy and the Austrian Empire. While at the library, Panizzi undertook the creation of a new catalogue, based on the "Ninety-One Cataloguing Rules" (1841) which he devised with his assistants. These rules served as the basis for all subsequent
catalogue rules of the 19th and 20th centuries. Panizzi had to give up his concept of "corporate main entry" to have his 91 Rules code approved. Panizzi's idea of corporate authorship later came to public attention through
Charles C. Jewett's code for the catalog of the
Smithsonian Institution in 1850. Panizzi was also influential in enforcing the
Copyright Act of 1842, which required British publishers to deposit with the library a copy of every book printed in Britain. ==Political activities and honours==