In his biography of Bruce Chatwin, Nicholas Shakespeare reveals that Philips was in fact David Bridges, son of Lucas Bridges who wrote one of Chatwin's favourite books on Patagonia, Uttermost Part of the Earth.
Chatwin frequently changed the names of the people he met to protect their identity (on this occasion at Bridges's request). That didn't stop some of them coming forward after its publication to complain that he had made things up. But according to Shakespeare, there was no fabrication in this instance. Bridges told him, 'I found it accurate. It's not flattering, but it's the truth.'