FitzRoy's intention was that they should be educated and converted to Christianity before being returned to their homelands, where they would be able to act as interpreters – with the aim of establishing friendly relations between their fellow countrymen and the British – and also use their new knowledge to improve the lives of their compatriots.

The crew's skirmishes with South American natives and a storm off the coast of Uruguay, presaged by wind-blown clouds of butterflies and moths, are beautifully managed set-pieces, pacy, gripping, and vividly chaotic”.

His account of the prickly friendship of the Tory prig Fitzroy and the cold-hearted Radical Darwin owes much to other novels of naval life and their forced intimacies; the spirit of Patrick O'Brian is often not far away”.

Thompson also portrays Darwin as more racist in the modern sense than Fitzroy, again by shuffling his deck of facts.” She concluded that “This Thing of Darkness is two sorts of book: a superior adventure story and a polemic.

One can enjoy the former considerably while noting that the manners of the latter are wanting.”[5] Robert Colvile, writing in The Observer was more impressed, finding: “The bare facts of Charles Darwin's voyage to the Galapagos, and his formulation of the theory of natural selection, are well known.

[…] While rarely lyrical, Thompson's prose drives the reader through the 750 pages with the unstoppable force of an ocean current, fusing brisk action, challenging ideas and gut-wrenching emotion into an astonishingly assured debut - and memorial”.