of the gentry following his marriage to Olivia Whitmore, Guinness became an agent for political change on behalf of Irish brewers. He served first as warden and later as master of the Dublin Corporation of Brewers, a position through which he would frequently argue on behalf of the brewing industry to the Irish Parliament. Of particular issue was the subject of the taxation of beer: in 1773, Guinness and fellow brewer George Thwaites petitioned the Irish House of Commons to change a restrictive taxation policy under which domestic Irish porter was taxed at a rate more than five times greater than beer imported from England. Four years later and amidst a greater crisis in British taxation policies caused by the American Revolutionary War, the House of Commons formally changed the tax code to no longer subsidise the Irish importation of English porter. This change created a market for the importation of Irish porter into England, and beer exportation soon became a staple of the Irish economy. Two years after the tax code was altered, Guinness became the official beer purveyor of Dublin Castle. Personal life Family On 17 June 1761, Guinness married Olivia Whitmore, a younger woman from a wealthy and well-connected family who offered him a £1,000 dowry. Whitmore was a descendant of William of Wykeham and had several socio-politically prominent relatives. One of these was her cousin Henry Grattan, a member of the Parliament of Ireland who argued in favour of aiding Catholics and gaining legislative independence in Ireland. With Arthur, Olivia Guinness suffered 11 miscarriages but gave birth to ten children, all but one of whom, Olivia, survived into adulthood. These four daughters and six sons were named, from oldest to youngest, Elizabeth, Hosea, Arthur, Edward, Olivia, Benjamin, Louisa, John Grattan, William Lunell, and Mary Anne. Elizabeth was born on 28 February 1763; by the time of Mary Anne's birth in 1787, Elizabeth was already married. Elizabeth Guinness married Frederick Darley in 1809, the same year that he became the Lord Mayor of Dublin. As Guinness's firstborn son, Hosea, born in 1765, was expected to inherit the family business, but he instead chose to enter the clergy. He was educated at Winchester College, the University of Oxford, and Trinity College Dublin before serving as the rector of St. Werburgh's Church, Dublin, until his death in 1841. Both Louisa and Mary Anne married into the clergy, wedding William