 Melvill for many years had the reputation of being "the most popular preacher in London", and one of the greatest rhetoricians of his time.First at Camden Chapel, then at St. Margaret's, and later on at St. Paul's, large crowds of people attended his ministrations.His sermon generally occupied three-quarters of an hour, but such was the rapidity of his utterance that he spoke as much in that time as an ordinary preacher would have done in an hour.