Partnership with James Davenport appears to be disolved by 1799.
Directories record Thomas Phelps as an Optician and Mathematical Instrument Maker located at 36, Fetter Lane, in 1799. 30, Red Lion Street, Holborn, in 1805. 33, Monkwell Street, Cripplegate, in 1817. 28, Holywell Lane, Shoreditch, in 1822. 19, Jewin Street, Cripplegate, also in 1822.
Thomas Phelps took over the business of James Stretch, Spectaclemaker, at Cock Court, St. Martin's le Grand, following Stretch's death in 1813.
His business was succeeded by Thomas Phelps (II).