After the sudden death of his elder brother Carl Frederick August on 9 May 1737, "Alexander", as he later called himself, became Crown Prince of the principality.

He evidently wanted to avoid supporting the Jewish banking houses that were then overseeing his financial affairs, and to keep as much of his revenue as possible in his own hands by setting himself up as a private banker.

One of Alexander's enterprises earned income from hiring auxiliary troops to King George III of Great Britain for the American Revolutionary War.

By December 1791, he had found a property near the River Thames, Brandenburgh House at Fulham, and in 1798, he acquired the Benham Park estate at Speen near Newbury in Berkshire.

On 15 December 1805, in the first Treaty of Schönbrunn, Prussia ceded the Principality of Ansbach to France in exchange for the Electorate of Hanover; in 1806, Ansbach was acquired by the Kingdom of Bavaria in exchange for the Duchy of Berg, and soon afterwards the Prussian defeat at Jena on 14 October 1806 resulted in the Principality of Bayreuth also being ceded to the French in the Treaty of Tilsit of July 1807.

In 1871, Bavaria became part of the new German Empire under the King of Prussia, but retained its internal independence, and it continues as a Land of the present-day Germany.