Given what we’ve learned about the caliphates over recent months – largely from the rise of the brutal Islamic State (IS) in the Middle East – the City of London, with its decidedly Western attitudes to money-making, is not where you’d expect to find one.

But it turns out the Square Mile is home to dozens of members of the world’s largest caliphate, the Ahmadiyya Muslim Community. With 10 million members scattered throughout 200 countries, it is currently the largest caliphate in existence. It is also the longest-standing – it was founded by caliph Mizra Ghulam Ahmad in India in 1889 and there have been four caliphs since then.

At the end of August the AMC came together in Hampshire: members flocked to a field near Alton for three days of prayers, food and mingling while pledging allegiance to their caliph Mirza Masroor Ahmad.

Huge tents were erected to house dining rooms, kitchens, prayer halls and bazaars. The tents were so big, one member proudly remarked that they had to be imported from Denmark.

As well as learning that the Danes need bigger tents than the rest of us, I found out the Ahmadiyya have been coming here for the past 48 years. But my obliviousness was not shared by the rest of the world – every event has been broadcast to 80 million people all over the world via Muslim Television Ahmadiyya.

The word “caliphate” has come to the fore in a negative context recently because of IS, but the AMC describes itself as a “peaceful Islamic movement”. Its founder claimed to be the Messiah prophesised in the Christian, Jewish and Islamic scriptures.

“The caliphate doesn’t have any political ambitions in the way many people view caliphates like IS and Boko Haram,” explains Usman Khan, a member of the caliphate who works as an IT consultant for a City firm. “We are not like IS – people have the wrong understanding of what a caliphate is.”

The word literally means a group of people who believe in the religious authority of a caliph, or “successor” to the prophet Muhammad. In the case of IS, the notorious Abu Bakr al-Baghdadi is considered to hold this title, whereas in the eyes of the Ahmadiyya community it is  Mirza Masroor Ahmad.