From 1839 onwards missionaries, both Roman Catholic and Protestant, arrived on the islands. At first they faced hostility, most notably with the killings of John Williams and James Harris of the London Missionary Society on Erromango in 1839. Despite this they pressed on, resulting in many conversions; however, to the consternation of the European, this was often only skin-deep, with Ni-Vanuatu syncretising Christianity with traditional "kastom" beliefs. The Anglican Melanesian Mission also took promising young converts for further training in New Zealand and Norfolk Island. Presbyterian missionaries proved particularly successful on Aneityum, though less so on Tanna, with missionaries being repeatedly chased off the island by locals throughout the 1840s–60s. The hostile response may have been partly to blame with the waves of illnesses and deaths the missionaries inadvertently brought with them.