Most British colonial railways, and even railways in Ireland (which was treated as a colony anyway) weren't built in standard gauge. Partly because the first were built when standard gauge wasn't yet standard even in core countries (prominent examples: the Great Western Railway in England and the Erie and Lackawanna railways in the USA had to be re-gauged later!), partly because these started out as isolated railways and there was one or other economic benefit to a different gauge.

The two most widely used British colonial gauges: the more wide-spread 'Cap-gauge' of 1067 mm (3'6") which allowed cheaper construction, and the broad-gauge of 1676 mm (5'6") which allowed higher loads and more stability against cyclonic winds. The latter was used by the British almost exclusively on the Indian subcontinent, but elsewhere also widely: parts of Argentina, Chile, Canada - and, also with the silly wind argument, the Bay Area Rapid Transit in California! (And the Iberian peninsula uses 1668 mm (5'5.5"), Russia and neighbours 1520-1524 mm (5'), Ireland has nd some parts of Australia had yet another broad gauge: 1600 mm (5'3"), and the Great Western had 2140 mm (7'0.25").)

To complicate matters, much of the Indian colonial network was narrow-gauge, but instead of Cap-, metre-gauge (3'3.37"). However, in today's India, there is an on-going major re-gauging programme from metre- to broad-gauge (and new lines are constructed in broad-gauge).

_{*Lunatic*, n.
One whose delusions are out of fashion.}