With the expiry of the patent in 1800 both Boulton and Watt retired from the partnership, each turning over his role to his namesake son. The two sons made changes, quickly ending public tours of the Soho Manufactory in which the elder Boulton had taken pride throughout his time in Soho. In retirement Boulton remained active, continuing to run the Soho Mint. When a new Royal Mint was built on Tower Hill in 1805, Boulton was awarded the contract to equip it with modern machinery. His continued activity distressed Watt, who had entirely retired from Soho, and who wrote to Boulton in 1804, "our friends fear much that your necessary attention to the operation of the coinage may injure your health".