Although not about Thames Tunnel business, this letter is unlike others in actually having "Thames Tunnel" given as the address. Marc Brunel's idea for the large scale manufacture of ships' blocks by machine is what had first brought him to England from New York in 1799. He had taken out a patent for his invention in 1801. Following long negotiations the government adopted his proposals in May 1803, and after still further delays the machinery was completed in 1806 at Portsmouth Dockyard. "The saving of labour and expense effected by the adoption of Brunel's ingenious mechanism was enormous. The system consisted of forty-three machines executing the various processes in the block manufacture, and by its aid operations which by the old method had required the uncertain labour of over a hundred men, could be carried out with precision by ten. The blocks were better than they had ever been before, and the estimated saving to the country in the first year after the machinery was in full working order was about 24,000l" (DNB).