Estates of Scotland responded to the Act of Settlement by passing the Act of Security, which gave the Estates the power, if the Queen had no further children, to choose the next Scottish monarch from among the Protestant descendants of the royal line of Scotland. The individual chosen by the Estates could not be the same person who came to the English throne, unless England granted full freedom of trade to Scottish merchants. At first, Anne withheld royal assent to the act, but she granted it the following year when the Estates threatened to withhold supply, endangering Scottish support for England's wars. In its turn, the English Parliament responded with the Alien Act 1705, which threatened to impose economic sanctions and declare Scottish subjects aliens in England, unless Scotland either repealed the Act of Security or moved to unite with England. The Estates chose the latter option; the English Parliament agreed to repeal the Alien Act, and new commissioners were appointed by Queen Anne in early 1706 to negotiate the terms of a union. The articles of union approved by the commissioners were presented to Anne on 23 July 1706 and ratified by the Scottish and English Parliaments on 16 January and 6 March 1707, respectively. Under the Acts of Union, England and Scotland were united into a single kingdom called Great Britain, with one parliament, on 1 May 1707. A consistent and ardent supporter of union despite opposition on both sides of the border, Anne attended a thanksgiving service in St Paul's Cathedral. The Scot Sir John Clerk, 1st Baronet, who also attended, wrote, "nobody on this occasion appeared more sincerely devout and thankful than the Queen herself". Two-party politics Anne's reign was marked by the further development of a two-party system. In general, the Tories were supportive of the Anglican church and favoured the landed interest of the country gentry, while the Whigs were aligned with commercial interests and Protestant Dissenters. As a committed Anglican, Anne was inclined to favour the Tories. Her first ministry was predominantly Tory, and contained such High Tories as Daniel Finch, 2nd Earl of Nottingham, and her uncle Laurence Hyde, 1st Earl of Rochester. It was headed by Lord Treasurer Lord Godolphin and Anne's favourite the Duke of Marlborough, who were considered moderate Tories, along with the Speaker of the House of Commons, Robert Harley. Anne supported the Occasional Conformity Bill of 1702,