Customs House including north bank of Purfleet Quay

Customs House built in 1683 to the designs of Henry Bell, located on the north bank of Purfleet Quay, King's Lynn.

The building is constructed of ashlar limestone from Ketton quarry with stone dressings and a plain clay tile roof below a lead-covered flat centre section. It is almost square on plan and follows the classical style. Originally designed as an open arcade with a first floor and attic under a hipped roof with an acanthus modillion eaves cornice, the arcade bays were blocked in the 18th century.

The north and south elevations are of five bays, while the east and west elevations have four bays, all broadly similar. The arcade bays are separated by Roman Doric pilasters supporting a plain Doric entablature and have keystones in the form of different masks, including those of Bacchus, the god of wine, and Ceres, the goddess of agricultural fertility, representing two of King's Lynn's main trading goods: wine and grain. The end bays feature two blind recessed panels placed vertically, except for the upper panel on the right-hand side of the south elevation which is glazed with leaded lights. The first floor is lit by mullioned and transomed cross casements with leaded lights in the middle bays, and single-light transomed casements in the end bays. The bays are divided by Ionic pilasters with garlanded capitals.

The north elevation has a broken-forward central bay with a heavy double-leaf panelled door. The entablature above bears a cartouche with the coat of arms of John Turner and a plaque dedicated to commercial and nautical business with the inscription: Mercaturx Reicp Nauticx Hoc posuit Johannes Turner Anno dom CDDCLXXXIII Arm. Above on the first floor is an arched niche containing a statue of Charles II on a fluted semi-circular pedestal flanked by a pair of Corinthian pilasters, with a shallow pediment over this bay. The east elevation arcades are filled in, as are those on the south elevation except for the central bay which has a double-leaf door with flush panels beneath a semicircular fanlight with radiating glazing bars and HL hinges on the internal side, providing access to the landing platform for the Customs' cutter. On the west elevation the arcade bays are glazed with leaded lights with radial glazing bars, possibly of 19th-century date.

The north and south roof slopes are lit by two pedimented dormers separated by a segmental-headed dormer. The east and west slopes have two pedimented dormers, all with two-light casements wholly within the roof space. Resting on the flat centre section is a timber lantern of Greek cross plan composed of four arches each carrying a pediment with angle pilasters and Corinthian capitals, surmounted by a hexagonal lantern with an ogee cap. The flat centre section has a turned balustrade with square corner piers, the eastern two of which disguise chimney flues.

The ground floor was originally open, with four bridging beams running north-south and one running east-west at the junctions of which were four entactic Doric columns resting on octagonal bases, of which the two western ones survive. The room in the north-east corner, once known as the King's Warehouse, has a wide panelled door with strap hinges and a lock case. The oak staircase and bolection moulded panelling were installed in 1718, though the lower flights were remade in the 1930s in the same style. The 18th-century upper flight has a closed and moulded string, dumb-bell balusters and a heavy handrail supported on square newels with flat square caps.

On the first floor, the Long Room occupies the western side and has large framed panelling, probably of 1741, with a dado rail and narrow horizontal panels along the top. A mark on the cornice indicates the former partition that was removed to create one large room. The east wall has two fireplaces: that on the left has a pulvinated frieze, moulded overmantel and stone flagged hearth; that on the right is now blocked up and has a simple moulded surround with a plain central panel. To the right of the fireplaces are built-in cupboards; that on the left retains HL hinges. The cupboard to the left of the right fireplace has been knocked through to create access to the Surveyor's Room which occupies the north-east corner. This has smaller-framed fielded panelling, probably dating to 1718, with a moulded dado rail and cornice, panelled window jambs, two-panelled doors and a fireplace composed of moulded stone jambs and entablature set directly into the panelling. The small room to the south of the staircase was used for storing wood for fires in the 18th century and retains some lead pipework.

The attic has been subdivided into small rooms, most of which have modern doors. The roof structure has principal rafters with butt purlins, and the cupola is supported on four cross-braced trusses.

The quay was probably a loading point of the Purfleet from the 13th century, and certainly a lime and stone quay existed in 1547. The present brick structure, laid in English bond with limestone dressings, results from continuous repair and rebuilding, with the earliest identifiable elements of 17th-century date. The listed section of quay begins at the south-east corner of the Customs House and runs 60 metres west along the north bank of the Purfleet, including the brick retaining wall, its stone capping and the stone steps leading down to the quay.