The Netherlands regained independence from France in 1813. In the Anglo-Dutch Treaty of 1814 the names "United Provinces of the Netherlands" and "United Netherlands" were used. In 1815, it was rejoined with the Austrian Netherlands and Liège (the "Southern provinces") to become the Kingdom of the Netherlands, informally known as the United Kingdom of the Netherlands, to create a strong buffer state north of France. On 16 March 1815, the son of stadtholder William V crowned himself King William I of the Netherlands. Between 1815 and 1890, the King of the Netherlands was also in a personal union the Grand Duke of the sovereign Grand Duchy of Luxembourg. After Belgium gained its independence in 1830, the state became unequivocally known as the "Kingdom of the Netherlands", as it remains today.