William Hallett was born on 10th April 1794 at Rotherfield. At the age of 17 he moved to Brighton as a carpenter and workman on the Pavilion but returned to Rotherfield with his first wife Mary Ann Miles whom he had married on 23rd November 1819 at Lewes. They had four daughters at Rotherfield before the family settled in Brighton and then two sons - William Henry Hallett (1828-1892) and Frederic Francis Hallett (1831-1901) both of whom were to have highly successful careers. After the death of his wife, Mary Ann, he was to marry Harriet Rebecca Ashmead in 1855 with whom he had three more sons.

William Hallett was one of the major builders of Brighton during the middle of the 19th century - including St John the Baptist church which was consecrated on 7th July 1835, The Bristol Hotel (named after the Marquess of Bristol his patron), The Victoria Wing on the County Hosptal in 1837, The Kemp Town Brewery in Seymour Street in the 1840s and much of the Eastern end of Brighton. William Hallett was prominent in public life from 1829 until his death in 1862 - as Director and Guardian of the Poor; High Constable; Alderman and from 1855-56 as Mayor of Brighton. He also played a significant role in local charities.

On 3rd April 1862 at 142 Marine Parade, Brighton, William Hallett died, aged 68. He was buried at St Denys Churchyard in Rotherfield where, in 1900, his eldest son from the second marriage John Hallett (1856-1904) erected a memorial and glass window to William Hallet and his wife Harriet Rebecca.