[1] Robertson arrived in the Gambia in 1832 as a surgeon for the Liberated Africans Department of the Gambian colonial government.
[2] He served under Richard Graves MacDonnell, Arthur Kennedy, Luke Smythe O'Connor, and George Abbas Kooli D'Arcy.
During the Soninke-Marabout War, when O'Connor's force was defeated at Bakkow Wood by a force of Marabouts, Robertson hastily armed a number of Government servants, merchants, and other loyalists, while sending messages of distress to Sierra Leone and Gorée.
[5] Robertson was summoned to speak before a Select Committee at the House of Commons in 1865 that examined the report on the governance of West Africa by Harry Ord.
Gray notes that Robertson had come "quite unprepared for a summons of this nature" and he suffered from not being able to "consult the necessary documents."