George I
George I was the king of Great Britain and Ireland, and duke of Hanover.
History
Per the Act of Settlement of 1701, Catholics could not succeed to the English throne. When Anne died in 1714, the crown passed over the Jacobite claim to George I. This established the Hanoverian dynasty and brought England into personal union with Hanover, and therefore the Holy Roman Empire.
Reign
In the early years of his reign, George held significant power in British governance and politics. His powers gradually devolved to the Parliament.
Hanover
George also established the Anglo-French Alliance with the very young Louis XV, a reversal of the geopolitical rivalry between England and France that had erupted as recently as the War of Spanish Succession.
These anti-British sentiments fueled factionalism within the Whigs. The Whig Split emerged by 1717, with Walpole and Townshend leading an opposition to Stanhope's government.
South Seas Company
The South Seas Company had been established by Anne's government led by Harley. The company had been granted a monopoly on slave trade in the southern Pacific and Atlantic, which attracted interest from private finance. The government sold shares in the company to buy back public debt, effectively consolidating the national debt into a chartered company. This was in the context of the very expensive War of Spanish Succession.
The company was already failing to turn a profit and post payments upon George's succession, but he (and many prominent Whigs) held significant stakes in the company--so they doubled down on the scheme and secured further financing. All Tories were removed from the company's board. In addition, the Whig Split emerged by 1717, and all oppositional Whigs were similarly removed. As a result, the company became tightly bound to the Whig government.
The bubble finally collapsed in 1720; the ensuing scandal led to mass dismissals and resignations from government.
Walpole's Government
Walpole, as one of the oppositional Whigs removed years earlier, emerged as the dominant remaining member of government. From this point, he is considered to be the first prime minister.
Legacy
George died in 1727 and was succeeded by George II. Despite acute rivalry over politics during his lifetime, George II ultimately pursued a very similar reign. to a large degree, this is a result of Walpole's government effectively being forced upon him, furthering the devolution of power from the crown to the Parliament.