Pembroke College is a college of the University of Cambridge, home to over six-hundred students and fellows, and is the third oldest of the colleges. Physically, it is one of the larger colleges in the university, and contains buildings from almost every century since its founding, as well as extensive and immaculately maintained gardens. The college is a financially well-to-do institution, and has a level of academic performance among the highest of all the Cambridge colleges. Not only is Pembroke College home of the first chapel designed by Sir Christopher Wren, but it is also one of the Cambridge colleges to have produced a British prime minister—no less than William Pitt the Younger. The college library, one of the finest in the university, with a Victorian neo-gothic clock tower, is endowed with an original copy of the first encyclopaedia to contain printed diagrams. The college's current master, Sir Richard Dearlove, was previously the head of the United Kingdom's Secret Intelligence Service.