Returning to London at the age of 16, he was engaged as a clerk by
Samuel Pepys Cockerell, architect and surveyor. Learning nothing there, as he thought, he ran away, and returned to his mother's lodgings, where he remained working hard for a year or more at the five
orders of architecture and French ornament and studying mathematics. When he was nearly 19
Henry Holland, the
Prince of Wales's architect in the alterations of
Carlton House and the
Pavilion, Brighton, received him into his house, and two years later offered him £60 a year for two years to enable him to pursue his studies at Rome. He had been introduced to Holland through his relative
John Linnell, who was in charge of one of London's leading cabinet-maker and upholsterer's firms and a rival to Thomas Chippendale. At Holland's office Tatham designed and drew at large all the ornamental decorations for
Drury Lane Theatre. The whole
proscenium was marked off from his drawings by
Charles Catton the younger, who painted the designs in fresco. The executed designs for the boxes in the theatre were by Linnell and they survive at the
V&A in the Print Room. Together with
Samuel Wyatt he also designed
Dropmore House in Buckinghamshire which was built in the 1790s for
Lord Grenville, later the Prime Minister who pushed through the law abolishing the slave trade. With Holland's help, and a loan of £100 from
John Birch, surgeon-extraordinary to the king, he felt justified in May 1794 in starting for Italy, travelling in company with his peer
Joseph Gandy. He spent his time industriously, chiefly in Rome and
Naples in company with Signor Asprucci, architect to
Prince Borghese and Don Isidoro Velasquez, an exhibitioner from the academy of Madrid, both, like Tatham, students of classical architecture. Tatham's chief friends during his stay in Italy were
Canova, Madame
Angelica Kauffman and her husband; Abbate
Carlo Bonomi, brother of Joseph Bonomi, RA ;
Sir William and
Lady Hamilton at Naples; and lastly,
Frederick Howard, 5th Earl of Carlisle, to whose long friendship and patronage he owed much of his success. He left Rome a month or so before
Bonaparte's first attack on the papal states in 1797; returning through Dresden, Berlin, and Prague, and making architectural drawings on the way. As the result of his studies he etched and published in 1799
Ancient Ornamental Architecture at Rome and in Italy. A second edition, containing more than a hundred plates, appeared in 1803, and a German translation was published at Weimar in 1805. His old master, Holland, had also commissioned him to collect in Italy antique fragments relating to ornamental architecture. He got together a noble assemblage, which was brought to England two years later. Tatham published a description of them in 1806. As of about 1895, they, along with his own collection of architectural drawings made at the same time, were in the
collection of Sir John Soane in
Lincoln's Inn Fields. Tatham first exhibited at the
Royal Academy in 1797, and continued to do so until 1836, contributing in all fifty-three designs. Tatham moved from 101 Park Street, Mayfair, first to York Place, and then to a house with a beautiful garden in Alpha Road, which he built for himself. He lived on intimate terms with
Thomas Chevalier, surgeon to
George III,
Benjamin Robert Haydon,
Samuel Bagster the publisher, and
John Linnell. == Designs ==