"in a private asylum"
18th Century Bethlem as portrayed in A Rake's Progress (1735)
Public Domain18th Century Bethlem as portrayed in A Rake's Progress (1735) - Credit: William Hogarth

While there were earlier institutions that housed the 'insane,' institutionalisation as the mechanism to treat (or contain) madness was essentially a 19th century phenomenon. 

At the start of the 18th century London's Bethlem (later called Bedlam), which had capacity for 100 inmates, was the only public asylum operating in England.  A second public charitable institution was opened in 1713 in Norwich.  From the mid-18th century the number of public, charitably-funded asylums grew. 

Partly as a result of the lack of state facilities, private madhouses proliferated in 18th century England.  Licensing legislation was introduced in 1774, which saw 16 private institutions recorded in London.