Named after former pupil Simon Marks son of Michael Marks, founder of the Marks & Spencer empire. It is just west of the main building, and was erected in 1958. Major extensions were made by addition of the first floor (after a gift of £50,000 from Lord Marks) and the Israel Sieff Lecture Theatre (after a gift of £5,000 from Lord Marks' brother-in-law), which were opened on 19 September 1962. It currently hosts the following departments: Physics, General Science (taken by Year 7 and 8 pupils – before the subject splits into the usual three divisions), Geography, Computing and Mathematics. There are five physics laboratories, including one for radioactive experimentation, on the ground floor. The main computer room is situated on the first floor of the Marks building.