Belsize, or Bel Assis in old French, means beautifully situated. The Manor of Belsize, a subdivision of the Manor of Hampstead, was left to the monks of Westminster in 1317. Henry VIII returned the estate to the newly constituted Dean and Chapter of Westminster in 1542 after the dissolution of the monasteries. In modern terms the estate extended from the top of Rosslyn Hill to England’s Lane and from College Crescent to Haverstock Hill, with additional land projecting east towards Parliament Hill.
By the middle of the 16th century, the estate consisted of a number of farms and a manor house. Belsize House, which stood in an irregular five-sided park, had 24 rooms including a hall, long gallery and great chamber. It was the only “aristocratic” house in the parish of Hampstead at that time. It was situated between the present day St Peter’s church and the junction of Belsize Park and Belsize Park Gardens. It could be reached from “The Great Road to Hampstead” by a carriage driveway along what is now Belsize Avenue.
The house was rebuilt in 1663 in the restoration style and two diarists, Samuel Pepys and Sir John Evelyn, recorded visits there.