The Portman Estate began to take shape in the 1760s, with Manchester and Dorset Squares among the first to be built. In the mid 1770s, work began on the Cadogan Estate in the manor of Chelsea, while the green fields of the Duke of Bedford's estate gave rise to Bloomsbury and Fitzrovia. The Bedford Estate contained 20 public gardens, all in the form of squares. Architect Thomas Leverton set a new trend with the first, Bedford Square, where all the houses were built to a unified design.
Crime and public disorder were an increasing concern in the late 18th century. Squares residents were often the victims of robbery and violence, and feared that squares could become a focus for riots. Security measures were stepped up, with watch patrols and extra lighting. During the Gordon Riots in 1780, troops assembled in squares and rioters burned down the house of the Lord Chief Justice in Bloomsbury Square.
Iron railings became increasingly commonly used, allowing views into the square but keeping the public out. In some places this improved matters: Grosvenor Square installed railings in 1774 in place of a high 'fence-wall', which had concealed the garden entirely. By 1800, Lincoln's Inn Fields was the only one of the great squares which was still open to the public.
Towards the end of the century, large numbers of garden squares began to be laid out in the landscape style, made popular by designers such as Capability Brown. This was the ideal of rus in urbe or bringing a part of the countryside into the town, as Thomas Fairchild had urged. The naturalistic style could be carried to extremes: Cavendish Square even had sheep grazing behind the railings in the manner of a grand country estate!
Some of the most famous landscape designers have worked on squares.
Charles Bridgeman, 18th century designer and gardener to royalty, is thought to have designed both Cavendish and St James's Squares.
John Nash, the architect responsible for Regent's Park and Regent Street, redesigned St James's Square a century later.
The well-known Regency designer, Humphry Repton, was involved in the design of Cadogan Place Gardens, and Bloomsbury and Russell Squares.
In the 20th century, garden designer John Brookes worked on Fitzroy Square garden and Dan Pearson on Bonnington Square, while Chelsea gold medal winner Christopher Bradley-Hole is designing the new Highbury Square on the site of the old Arsenal football stadium.