Built as Paradise House, or Newington Park House, in the late 1700s for Jonathan Hoare. William Crawshay (1764 – 1834) bought it in 1811. He objected to his daughter's choice of a husband so it was not until his death, that Eliza (or Elizabeth, depending on source) married the Reverend Augustus Clissold, in 1835, at which the house and estate became his property and so were renamed after him. Eliza died in 1877 and Augustus in 1882. They had no children so the estate reverted to the Crawshay family.
Eliza had a brother George and he may be the George Crawshay who in 1886 tried to develop the estate but public opposition prevented this. The story of the 4-year long campaign by the Clissold Park Preservation Committee, led by Joseph Beck with John Runtz, is told at Saving Clissold Park.
The Metropolitan Board of Works purchased the estate in 1888 and it was opened to the public on 24 July 1889 by the Earl of Rosebery, Chairman of the new London County Council, the MBW's successor. The two lakes are called respectively Beckmere and Runtzmere.
In 1893 Eliza's nephew's wealthy widow, Rose Mary, erected on Clissold Park house, a water fountain in memory of her three dead baby sisters.
Information from: Wikipedia, London Gardens Online, Clissold Park User Group, Saving Clissold Park.
Beck preserved the paperwork of the campaign and this is now available to see at Saving Clissold Park.