Inside the mansion are a number of richly decorated state rooms; of the interior features, only the hall, the staircase tower and the chapel are Gothic in design. The high staircase hall features a stone stair with iron railing, surrounded by niches containing statues by Sir Richard Westmacott. At the centre of the fan-vaulted ceiling is a large dial connected to the weather vane on the roof which displays the current wind direction. The Brownlow Hall contains a giant frieze of the goddess Venus surrounded by putti with an armorial centrepiece and three early-Twentieth Century murals. Redecoration of the interiors was commissioned by Lady Marian Alford and executed in the neoclassical style in 1855–63 by Sir Matthew Digby Wyatt, including a replica of Guido Reni's Aurora ceiling and aedicular door surrounds. Among the alterations carried out after the conversion of the mansion into a college, the conservatory was altered by Clough Williams-Ellis in 1919 to form a dining-room. The boundary between Hertfordshire and Buckinghamshire originally passed through the dining room, though the house is now entirely in Hertfordshire.