Main Library was part of the Great Court buildings designed by Hennessy and Hennessy in 1935-1936. It consisted of two floors with a glass ceiling in the light well in the centre. Main Building was designed to be extended with an additional three floors, with high ceilings and a large light well in the centre. When the Library had insufficient space for students and books it was decided to go ahead with the extension of three more floors, as specified by Hennessy and Hennessy. Birrell proposed five additional floors instead of the three, the installation of passenger lifts, fluorescent lighting, and air-conditioning. Birrell was responsible for the internal arrangement and finishes. This file comprises 15 plans for alterations and additions to Main Library. Includes: sketch of lower ground floor (now Level 1), working drawings for 1st to 5th floors (now Level 3 to Level 7), stair details and compactus shelving.
Main Library was later known as Undergraduate Library; with the construction of Central Library in 1971 its name was changed to Duhig Building; and later, around 2000, to Duhig Tower.