It is said that Thomas ‘spent the last seven years of his life in bed’, confined to his room at 22 Henry Street, Pentonville. He was there as ‘John Salmon’ when the Census was taken in 1851 and he died at that address as Thomas Hay Allen on 14 February 1852. He was buried in that name at St Giles in the Fields, Middlesex, on 23 February 1852, aged 84. His son, Charles, in order to distance himself from him, wrote in 1877 that his father was called James and had died in 1839. Some believed that he was buried at Old St Pancras, Middlesex (as stated in the introduction to the 1892 edition of his sons’ "The costume of the clans", xvii, and repeated in the "Dictionary of National Biography") and Beveridge added ‘but the stone said to have been placed over his grave cannot now be found’.