then moved to Birmingham, where the elder Matthew Boulton made his son a partner at the age of 21. Though the son signed business letters "from father and self", by the mid-1750s he was effectively running the business. The elder Boulton retired in 1757 and died in 1759. The Boultons had three daughters in the early 1750s, but all died in infancy. Mary Boulton's health deteriorated, and she died in August 1759. Not long after her death Boulton began to woo her sister Anne. Marriage with a deceased wife's sister was forbidden by ecclesiastical law, though permitted by common law. Nonetheless, they married on 25 June 1760 at St. Mary's Church, Rotherhithe. Eric Delieb, who wrote a book on Boulton's silver, with a biographical sketch, suggests that the marriage celebrant, Rev. James Penfold, an impoverished curate, was probably bribed. Boulton later advised another man who was seeking to wed his late wife's sister: "I advise you to say nothing of your intentions but to go quickly and snugly to Scotland or some obscure corner of London, suppose Wapping, and there take lodgings to make yourself a parishioner. When the month is expired and the Law fulfilled, live and be happy ... I recommend silence, secrecy, and Scotland." The union was opposed by Anne's brother Luke, who feared Boulton would control (and possibly dissipate) much of the Robinson family fortune. In 1764 Luke Robinson died, and his estate passed to his sister Anne and thus into Matthew Boulton's control. The Boultons had two children, Matthew Robinson Boulton and Anne Boulton. Matthew Robinson in turn had six children with two wives. His eldest son Matthew Piers Watt Boulton, broadly educated and also a man of science, gained some fame posthumously for his invention of the important aeronautical flight control, the aileron. As his father before him, he also had two wives and six children. Innovator Expansion of the business After the death of his father in 1759, Boulton took full control of the family toymaking business. He spent much of his time in London and elsewhere, promoting his wares. He arranged for a friend to present a sword to Prince Edward, and the gift so interested the Prince's older brother, George, Prince of Wales, the future King George III, that he ordered one for himself. With capital accumulated from his two marriages and his inheritance from his father, Boulton sought a larger