It was 1703 and the 18-year-old Georg Friedrich Händel had arrived in the North German city of Hamburg, known even then as something of a den of iniquity. “The great Business of the place is commerce and Drinking,” wrote an Englishman of the day, a fact that likely appealed to a lively young Saxon with a fondness for the bottle.

Hamburg, c.1700

Hamburg’s other great business was music – opera in particular – and Händel, as he was known before the English robbed him of his umlaut, soon found himself a cushy billet in the orchestra at the Gänsemarkt playing second violin under the watchful eye of maverick musical director Reinhard Keiser. When young Georg wasn’t fiddling away, he was doing the rounds of the local churches and it was in one of them that he bumped into another young hopeful. Johann Mattheson was a fellow composer, a fledgling music critic, and would soon become an influential diplomat.

The two hit it off at once and soon became firm friends, enjoying boating trips on the Elbe and composing double...