On Monday September 18, 1876, two Victorian clergymen of the Church of England were on board a steamer on the River Sava, travelling to Belgrade. Both men, it is probably fair to say, were full of indignation and very excited. Eastern Europe was on the edge of war and their journey was an investigation into reports of Bulgarian atrocities the previous spring when Ottoman irregular troops (themselves Circassians recently expelled by Russia from their homeland) had put down an uprising by killing several thousand Bulgarians.

Our two clergymen had spent the previous evening as the guests of Bishop Josip Strossmayer, Catholic Bishop of Bosnia but also a militant Slav nationalist. Strossmayer had told them stories of Turkish cruelties, his strongest claim apparently (though he would never afterwards confirm that he had actually said so) being that the Turks had impaled pregnant Christian women. With the bishop’s words ringing in their ears, the two men asked the steamer’s crew about impalement. Had they ever seen such a thing? The sailors solemnly assured them that they had often seen human beings writhing on stakes and that the latter were used by the Turks to impale their prisoners. In later years sailors on the river steamers would be questioned about this incident on many occasions. They invariably told visitors that the two credulous Englishmen had been the butt of a joke.

While the horrified travellers were considering the sailors’ claims, their boat passed some poles, 6 metres high, standing in the water near a military outpost on the Ottoman side of the river – used, according to later travellers, for agricultural and fishing purposes. Whether or not they were the victims of a hoax, the two Englishmen believed that they were looking at impalement. The younger of the two, Malcolm MacColl, would later declare that he had seen a body on one pole, still alive and writhing. His companion, Canon Henry Liddon, a former Oxford professor and canon of St Paul’s Cathedral, was not quite so definite but backed him up whenever required to do so. On reaching Belgrade, MacColl immediately wrote a vehement letter to The Times, denouncing the “cruel rule of the Turk”, who “feels he can indulge in safety his unbridled passion for cruelty”.

This was the first shot in a controversy that would erupt at intervals in the letters column of The Times for the next 11 years. MacColl was quickly challenged – by the local British consul, by travellers the Balkans and Turkey. But he was backed by others, though most of these were already political opponents of the Ottoman Empire and supporters of the Slav movement. Initially MacColl seemed to win the debate and convinced the horrified Victorian public. A decade later, however, the attitude of the public and the press was openly sceptical and disbelieving. Later still, in the 1890s, although MacColl – who by then was Britain’s leading opponent of the Turks – still clung to the story of the impalement and the corpse on the pole, this was only brought up by others to mock him. But that hardly mattered. By the late 1890s, public opinion in Britain – thanks to the efforts of MacColl, above all others – had settled firmly into a groove of hostility towards the Turks that would last well into the 20th century. That boat ride on the Sava was a historical turning point.

When The Times reported on June 5, 1878, that definite cases of impalement of Muslims by Bulgarians had been authenticated by British diplomats at Dedeağaç (today Alexandropolis), no one in London seems to have taken much notice.

Back in the late summer of 1876, MacColl and Liddon had been newcomers to the Eastern Question. Their interest was only a couple of months old, triggered by newspaper revelations in July of the terrible events in Bulgaria in the late spring. But they acquired an agenda very quickly. In mid-August, Liddon had preached a famous sermon in St Paul’s warning Benjamin Disraeli’s pro-Ottoman British government that support for the Turks amounted to sin. About a week later, on August 21, MacColl urged his close friend and patron, William Gladstone, to take up the question of the Bulgarian atrocities.

MacColl and Liddon were almost certainly already in touch with Russians and Serbs in London eager for strong support from British public opinion against the Ottomans. At the house of Madame Olga Novikoff, a Slavophile writer and propagandist and a friend of Gladstone’s, MacColl met the Russian ambassador and would have come into contact with Russian views. He was also apparently in contact with representatives of the Serb nationalist movement in London, for in Belgrade he and Liddon stayed at the home of Philip Christitch (Hristi), the main Serbian official who had been lobbying on behalf of the Serbian national cause in London since 1863.

The Russians were poised to launch a war of liberation in the Ottoman Balkans and Britain had long been extremely fearful of Russian expansion into the Ottoman lands. Whatever liberal public opinion made of the dead Bulgarians, the sympathies of Queen Victoria and Prime Minister Benjamin Disraeli were on the side of the Turks. Disraeli’s government was less committed, with four ministers opposed to support for Turkey, but it was only a little over two decades since Britain had blocked Russian moves against the Turks by going to war in the Crimea. So the Russians needed to win friends in British society and to discredit the Turks; publications arguing their case began appearing in London.

Over the following decade MacColl would emerge as the doyen and most energetic organiser of the movement against Turkey and an outspoken advocate of the “ethical foreign policy” of allying with Russia to break up Turkey. In 1876 he had been merely the 45-year-old vicar of a small and obscure church who had won a name for himself in London high society with his writing. It was an impressive achievement. MacColl was a self-made man, and though he had studied to become a clergyman, on most matters he was entirely self-taught.

The son of a very poor Scottish Highland family in Argyllshire, he had extricated himself from provincial obscurity as a young man by writing to Gladstone in 1858 on a theological issue. In the resulting exchange of letters, the unknown and poverty-stricken MacColl somehow skilfully persuaded the statesman to help him to move to London and to transfer into the Church of England. Several brothers and sisters seem to have moved with him.

Once in the capital, MacColl had almost immediately begun turning out a flow of highly readable and articulate books and pamphlets, though until 1876 these were almost always on church matters or in support of Gladstone. Several were dedicated to Gladstone for, though the politician was 22 years his senior, MacColl had become his personal friend, confidant and ultra-loyal supporter, invited at regular intervals to stay at Hawarden Castle, the Gladstone family’s country seat. In London, MacColl would sometimes visit Gladstone twice in a day, and he remained a very close family friend for the rest of his life.

His personal situation, however, was fragile. In 1874 Gladstone, then prime minister, had managed to get him a living at a small church, St George Botolph Lane, in the City of London. There was little work to do there – he had a tiny parish of only eight worshippers and used part of his income of £600 a year to hire a deputy. But St George’s was due to be knocked down and when that happened the income of its rector would disappear.

By 1876 Gladstone was 65 years old and temporarily on the sidelines of politics. After resigning as prime minister two years earlier, he had given up the leadership of the Liberal Party, apparently swapping politics for theology and Classics. A brilliant classicist, he had always been strongly Philhellene.

Gladstone had, however, been hesitant over taking up the cause (to which MacColl had already become a strong convert) against the wishes of his seniors in the Liberal Party. On August 26, a few weeks before his departure for Serbia, MacColl wrote to Gladstone, then still apparently undecided over whether or not to defy his party bosses and campaign. He urged Gladstone to take up the Eastern Question. “Do, please raise your powerful voice against the bestial government of Turkey and the degrading policy of our own government,” he wrote.

Just before he and Liddon set off on their journey, MacColl put together a bundle of press cuttings and information for Gladstone to make use of. His mind made up, Gladstone, after a few feverish days of writing, published a 64-page pamphlet on September 6: Bulgarian Horrors and the Question of the East.

The pamphlet, an instant bestseller, became one of the most famous documents of the 19th century. Forty thousand copies were sold in four days, 200,000 in the first month. It denounced the Ottomans with a mixture of religious and racial fervour – “No government ever has so sinned, none has proved itself so incorrigible in sin, or which is the same, so impotent in reformation” – and branded the Turks “the one great anti-human specimen of humanity”.

Gladstone had ignited a blaze of protest. Three days later he made a great speech on the atrocities, at Blackheath, the first of many “indignation meetings” that autumn. For three months hundreds of demonstrations against the pro-Turkish prime minister, Benjamin Disraeli, and the Turks took place in towns and villages across England.

Such was the background against which MacColl stepped to the fore in the anti-Turkish movement in the autumn of 1876. His stream of impassioned letters in The Times about his sighting of an impalement helped build up the torrent of public indignation. And his details grew more, rather than less, specific as time went by. On his own account, he was also doing a great deal more behind the scenes.

Years later, writing to Arthur Balfour, MacColl would boast that the agitation had all been his doing, the work of a vast secret association of Anglican priests. The boast must have been an exaggeration, since many of the meetings were organised by Non-Conformist churches with whom MacColl had little sympathy. But for the rest of his life he remained one of the most prominent names in anti-Ottoman committees and groups, and his name became a byword for hostility towards the Turks.

The main effect of MacColl’s 30-year-long campaign was to make it very unsafe for any British consul in the Ottoman Empire to write despatches that portrayed Christians sometimes as aggressors and Muslims as victims. Those unwise enough to do so ended up, like Sir Alfred Biliotti, having public meetings organised against them in London and being discussed in the House of Commons. In the mid-1870s Turks were seen as an empire on the edge of Europe. By 1900, they were viewed as something close to demons.