Islamic prayers were due to be recited in Istanbul’s great monument yesterday for the first time for 85 years. Diplomatic history helps explain why the pain at the reconversion of the former Christian basilica into a mosque runs so deep in the Orthodox world

The first few weeks of 1923 saw fateful developments for the city on the Bosphorus. All those events are worth studying for anyone who is trying to understand the change that is now taking place in one of the world’s greatest monuments, Hagia Sophia, and its likely effect on the Eastern Christian world.

In that tense post-war winter, High Commissioners from the Western powers continued to wield influence in the metropolis they called Constantinople. But they were due to withdraw in nine months, and the shape of the new order was the topic of furious bargaining on a Swiss lakeside.

With hope, anger and apprehension, people in Istanbul struggled to follow what was happening in Lausanne. Europe’s diplomatic masters were fine-tuning a population exchange between Greece and the new Republic of Turkey, the successor of the defunct Ottoman Empire, under which most religious minorities would be transferred to “their” country: Muslims from Greece to Turkey, Orthodox Christians, if not in flight already, from Turkey to Greece.