Despite limited knowledge of foreign languages, MacColl corresponded with continental Roman Catholic dissidents after the First Vatican Council: Josip Juraj Strossmayer of Diakova, and Ignaz von Döllinger in Munich.

This, as well as similar currents of opinion in the Liberal Party, may have been responsible for MacColl's own interest in combatting Turkish political power during the last three decades of his life.

In August 1876, soon after the exposure of the killings of up to 15,000 Bulgarians the previous spring by Circassian irregulars in the Ottoman army, MacColl and Henry Liddon of St Paul's Cathedral travelled to Vienna and Serbia on a fact-finding tour.

Though their testimony could not be independently confirmed, and was challenged by the local British Consul who suggested that the object in question might have been only a bag of beans, MacColl and Liddon used this sighting as proof of the iniquity of Turkish rule in the Balkans.

This fitted in with a theme in their sermons that those in Britain (such as Gladstone's arch-opponent Benjamin Disraeli) who did not actively oppose Turkish rule were themselves guilty of its sins.

MacColl maintained a large house at Kirby Overblow, south of Harrogate, and continued to devote himself to political pamphleteering and newspaper correspondence, the result of extensive European travel, a wide acquaintance with the leading personages of the day, strong views on ecclesiastical subjects from a high-church standpoint, and particularly on the politics of the Eastern Question, the uprising in Crete, then still an Ottoman province, the cause of the Armenians and Islam.

During the Greco-Turkish War of April 1897, he visited Athens to confer with the King, conveying the monarch's private views both to Gladstone and also to the Prime Minister Lord Salisbury.

Major works include: MacColl's research usually relied on British Blue Book collections of consular despatches, written up in a prosecutorial style.