Northern Part of Mostyn Hotel

The northern part of the Mostyn Hotel, formerly listed as No 16, is an end of terrace former town house built around 1768-1770, with 19th-century alterations. It is possibly designed by Abraham and Samuel Adams, who constructed several houses nearby on the southeast and west sides of Portman Square. The building is made of brown brick and features a slate roof, rising four storeys with a dormered mansard and a basement. It has five windows across the front and a long return to Seymour Street.

The entrance includes a semicircular arched doorway in the second bay from the left, which is sheltered by a 19th-century stuccoed Doric porch. The windows are recessed sashes set under flat gauged arches. There are stucco plat bands and a sill band at the first floor, along with a cornice above the second floor and a cornice capping the parapet. The first floor is adorned with cast iron balconettes, and there are 19th-century cast iron area railings. The return side of the building has similar architectural details, but the ground floor features stucco rustication.

Inside, the building retains some fine delicate stuccowork ceilings and mouldings in the Adam style. The southern part of the hotel, which faces Bryanston Square, is not considered of special interest.