MacDonnell, Alexander (1798–1835), chess master, was born in Belfast, son of Alexander MacDonnell, doctor. Educated locally, he began a successful career in business, spending ten years as a merchant at Demerara in the West Indies (1820–30). Moving to London around 1830, he wrote pamphlets on political economy, and was appointed secretary to the West India committee of merchants. Now a wealthy man, he was taught the intricacies of the game of chess by William Lewis (1787–1870), one of the leading players in the United Kingdom. He quickly excelled at the game, and soon Lewis was refusing to play competitively against him for fear of damaging his reputation. When the Westminster Chess Club was formed in 1833, MacDonnell was widely recognised as the best player in Britain.
At this time Louis de Labourdonnais (1795–1840) of France was regarded as the greatest player in the world, and in 1834 he went to London to challenge MacDonnell to confirm his supremacy. Between June and October 1834 the two men played six matches (85 games), in a titanic contest that was unparalleled in the nineteenth century, and which is credited with raising the profile of the game internationally. Unlike his opponent, MacDonnell had a slow and thoughtful style, and he measured the implications of every move carefully. Nevertheless his play contained flashes of genius, and he would leave the playing sessions exhausted, sometimes obliged to spend the night walking around his room to calm down. The series began with three lengthy draws, but eventually the weaknesses in MacDonnell's technique were exposed and he lost 45, won 27, and drew 13 of the games. The unofficial world championship was never concluded formally, however, as Labourdonnais was recalled to Paris, and during his absence the stress took its toll on MacDonnell and he fell ill and died.
Described as ‘quiet, reserved, [and] outwardly imperturbable’ (Hooper & Whyld, 197), MacDonnell was regarded as one of the greatest players of the century. Many of his games are extant, including the six matches with Labourdonnais that were recorded by William Greenwood Walker, the secretary of the Westminster Club, who sat beside MacDonnell and wrote down every move, scarcely ‘daring to breathe lest the conceptions of his hero should miscarry’ (Hartson, 19). MacDonnell died 14 September 1835 of Bright's disease, and was buried at Kensal Green cemetery, London. He never married.