By the middle of the nineteenth century, the Witchfinder Army was well on its long slide into obsolescence and decrepitude as a forgotten corps of the British Army. Attitudes to witches were getting depressingly liberal – either nobody seriously believed in them any more, or the growing social practice was to collect batty old women together and get some useful work out of 'em down the workhouse, rather than all that wasteful burning nonsense that belonged to a different century. (Although Ireland, a colonial outpost that remained a couple of hundred years adrift of the present day, burnt its last witch in 1894. Strange but true.)
The Witchfinder Army, however, enjoyed a strange renaissance in the latter part of the century, as the British Empire grew to bloatedness, with colonial adventurers expanding the Indian Empire into Burma and the Arabian Peninsula, and snaffling those last few useful bits of Africa before the damn French, or worse, the bloody Belgians, got there first. Not to mention those Johnny-come-latelies, the Italians and the Germans, who were jolly welcome to the scrubby deserty bits around the edges that nobody in their right mind would ever want, like Libya and Namibia.
This put British forces up against a different force of Witchery, either in the form of African witch-doctors and jujumen, or swarthy priests worshipping jewel-eyed little green gods with too damn' many arms. Not that this would disconcert your British soldier too much, as Tommy Atkins is the salt of the earth and anyway bound to have had some sort of sensible Christian education. No, that sort of thing has the power to frighten the natives and spook the colonial troops, so we need big magic of our own to counter it.
Enter Regimental Sergeant Major Nurker of the Witchfinder Army, and others of his ilk, who were discreetly attached to various colonial armies to provide a show and a presence.
As related in Good Omens, six foot seven and eighteen stone, the presence of Nurker, with his specially reinforced Bell, his very large Book, and imposing three-foot Candle, together with exorcisms boomed in a voice audible in Johannesburg, was said to clear the South African Veldt of jujumen, tribal shamans, witch doctors and Zulu Royal House Witches for several miles in every direction, and white man's medicine was seen to prevail by all. Indeed, Cecil Rhodes himself said of Nurker that he was worth a battalion of Gatling guns to me.
Regimental Sergeant Major, the most senior NCO in any unit, is a feared rank in the British army. American readers: think Gunnery Sergeant with God-like powers and the fear and respect of all around him – including the officers.