Short answers, pulled from the story.
Captain Swing was not a real person. The name was an invented pseudonym appended to threatening letters sent to farmers during the Swing Riots of 1830 in rural England. Authorities tried to identify and apprehend "Captain Swing" before eventually accepting that the name was fictional.
The Swing Riots were driven by a combination of unemployment among men returning from the Napoleonic wars, wage undercutting by itinerant Irish labourers, falling agricultural prices, the end of the custom of gleaning leftover crops, church tithes, the enclosure of common land, and the introduction of threshing machines that displaced farm workers.
Around 2,000 protesters were brought to trial in 1830-1831. Of those, 252 were sentenced to death, though only 19 were actually hanged. Some 644 were imprisoned, and 481 were transported to penal colonies in Australia.
The origin is uncertain. The word "swing" may refer to the swingel, the part of a threshing flail that beats corn from the ear. It may also evoke a body swinging from the gallows. A third explanation is that agricultural work-party leaders would shout "Swing!" to signal the resumption of work, and were customarily called Captain.
The word "Swing" was graffitied on walls between Canterbury and Dover by the 18th of September 1830, following a threshing machine attack in the Elham Valley, Kent on the 28th of August 1830. Threatening letters signed SWING were also sent to local farmers at the same time. Earlier anonymous letters threatening farmers in the Reading area over threshing machines date back to 1811.
Captain Swing appeared as a real character in the alternative reality novel The Difference Engine, as a secret police captain named "Findthee Swing" in Terry Pratchett's Night Watch, and as the protagonist of Warren Ellis's graphic novel Captain Swing and The Electrical Pirates Of Cindery Island. Peter Whelan's stage play Captain Swing was produced by the Royal Shakespeare Company in 1979, and Michelle Shocked released an album called Captain Swing in 1989.