The Jalsa Salana is organised by the Ahmadiyya Muslim Community, which has its main base at the Baitul Futuh Mosque in Morden.
The annual event attracts more than 40,000 attendees from nearly 100 countries and is run by 7,000 volunteers.
Fareed Ahmad is the National Secretary of the Department for External Affairs for the community.
He explains why so many want to get involved.
