William had three sons, including Robert, who later entered the 83rd Regiment of Foot, reached the rank of captain and married Catherine, the daughter of Ralph Babington, of Greenfort, County Donegal, in 1791.

[1] Having then lived for two years in Surrey, followed by seven in Scotland, Hay then came to London, where on 10 December 1839 he took up an appointment as the first inspecting superintendent of the Metropolitan Police.

This post was effectively the chief deputy to the two joint commissioners, Lieutenant-Colonel Sir Charles Rowan and Richard Mayne, and broke the rule established by Sir Robert Peel that, apart from the two commissioners, all police officers should be promoted from the ranks.

[citation needed] In 1850, on the retirement of Sir Charles Rowan, Hay was made one of the joint commissioners of the Metropolitan Police and sworn in as a Justice of the peace.

He was particularly angered that Mayne took personal charge of the policing of the Great Exhibition in 1851, a job which Hay, as a military man, thought should have gone to him.

[7] In 1852, the crowds coming to pay their respects at the lying-in-state of the Duke of Wellington got out of hand and it was reported that one or two people had been crushed to death.

[citation needed] There was criticism of the police, and Hay had a paragraph inserted into the newspapers claiming that Mayne had been responsible.