P.C. Keytel, manager of the Fresh and Cured Fish Company in Cape Town, became a member of the South African Philosophical Society in 1905, but was no longer a member by 1907. He was a friend of the South African Museum and therefore received the publications of the museum free of charge. In 1908 P. Casper Keytel, presumably him, applied for permission to collect guano on Tristan da Cunha, in the south Atlantic. During a year's stay on the island during 1908-1909 he made a valuable collection of animals and plants which he presented to the South African Museum in Cape Town. The collection, which formed the basis of a special exhibition of the natural history of the island group, included eggs of sea birds, nine species of fish, a small collection of molluscs, and 65 species of plants, some of them endemic to the island. Keytel also made notes on the arrival of sea birds.
In 1913 E.P. Phillips* published "A list of the phanerogams and ferns collected by Mr P.C. Keytel on the island of Tristan da Cunha, 1908-1909" in the Annals of the South African Museum (Vol. 9(3), pp. 96-1030).
By 1908 Keytel resided at Sandown House, 5 Beach Road, Mouille Point. The next year his house had been renamed "Tristan". He was no longer listed as a resident of Cape Town in 1910. His full names appear to have been Peter Casper Keytel, who died in 1959. However, there was also a Pieter Casper Keytel (who died in 1937) living in the Cape Colony at the time.