Sultan was born in Kabul in 1881, moved to India to study Islam, and became involved in polemics against other religions. During his hajj to Mecca he started to reflect on eternal salvation and wether or not Islam could actually provide it. He reflected on the hadiiths where Muhammad says that he cannot save anyone at all, even through his intercession. Then he found the verse in Matthew where Jesus issues the great invitation: 'Come to me all you heavy-laden, and I will give you rest....' He accepted.
In 1903 he requested baptism, and eventually received the sacrament of Holy Orders in the Anglican Church.
More can be read about him in Called from Islam to Christ by Fr. Jean-Marie Gaudeul. Or, if you are particularly resourceful in terms of finding books: Why I Became a Christian which he himself wrote (Gospel Literature Service, Bombay: 1978).
His entire testimony can be read HERE.