In 1965, it became part of the London Borough of Barnet and in the early 21st century was converted to residential housing as Princess Park Manor and Friern Village.

[1] At its height, Colney Hatch was home to 2,500 mental patients and had the longest corridor in Britain (It would take a visitor more than two hours to walk the wards).

The asylum with its surrounding fields, gardens and recreation grounds adjoined Friern Barnet Road and is shown on the Ordnance Survey map of 1868–1883, which labels the nascent settlement of New Southgate under a popular developers' name Colney Hatch Park.

Friern Barnet is today used fairly interchangeably with New Southgate for the area west of the Great Northern Railway – a short path from the asylum led to the station built to serve it, New Southgate railway station, which moved a short distance and remains.

[2] Colney Hatch was the southern hamlet, centred on a crossroads, of the medieval parish of Friern Barnet which stretched 3 miles (4.8 km) north north-west and was half as wide as long.

[4] The architect was Samuel Daukes, whose Italianate corridor-plan design was based on the advice of John Conolly, the superintendent of the First Middlesex County Asylum.

In 1896, a temporary building of wood and corrugated iron was erected to house 320 chronic and infirm female patients in five dormitories, despite warnings from the Commissioners in Lunacy that this would pose a serious fire risk.

[2][10] In its place, between 1908 and 1913 seven new permanent brick villas were built: four for the survivors of the fire, one for subnormal boys with epilepsy or disturbed behaviour and two for patients with tuberculosis or dysentery.

[5] During the Second World War twelve wards were requisitioned for use by the Emergency Medical Service (EMS) to be run by St Bartholomew's Hospital.

Patients were able to earn up to 16/- (80p) 'pocket money' per week to spend in the café and hospital shop by working on the wards, kitchen and laundry.

A Committee of Enquiry held in 1966 found that the hospital accommodated 708 patients over the age of 60 years, of whom 253 (36%) were not considered by clinicians to be in need of psychiatric care.

The Committee rejected entirely the allegation that everything in Friern was arranged for the benefit of the staff, including the suggestion that "the Physician Superintendent was seldom in the hospital for more than one or two hours a day".

[11] The hospital's internal broadcasting service started in 1971 after funds were raised by Minchenden Grammar School.

Radio Friern moved to a new studio in premises originally occupied by the hospital dentist in 1975 increasing its broadcasting hours by the early 1980s to include programmes airing six days a week.

"[17] The asylum is referenced (as a byword for madness) in chapter 8 of the children's novel The Magician's Nephew, part of the Chronicles of Narnia by C.S Lewis: when Jadis proclaims herself as an Empress and demands that residents of London bow to her, they jeeringly respond by saying in Cockney dialect, "Three cheers for the Hempress of Colney 'atch!

[21] In G. K. Chesterton's The Man who was Thursday, the asylum is again referenced as a byword for madness in the following dialog: “Your offer,” he said, “is far too idiotic to be declined.