In his book The Return of a King, historian William Dalrymple is strongly critical of British policy toward Afghanistan prior to the disastrous invasion of 1839. He implies, quoting the British envoy William Burnes, that the British could have successfully bought the rulers of both Afghanistan and the Punjab on-side.
While I see no reason to doubt the suggestion that the ruler of Afghanistan, Dost Mohammed, was pro-British, his price for a formal alliance was British help in reclaiming Peshawar from the invading Punjabi forces. Given this friction between the two states, the idea that diplomatic solution was not just feasible but relatively easy, seems a bold one.
"Relatively easy" is difficult to qualify without extensive quotes from the book, as it's implied in tone rather than stated directly, but here's an example:
This, he [Burnes] realised, was actually good news for his mission, as it could only make Ranjit Singh [the Punjabi ruler] more willing to come to terms with Dost Mohammed about the future of the city, and with luck allow Burnes to reconcile the two rivals, bringing both into alliance with the British.
Reading around the subject - see James Perry in Arrogant Armies for example - it seems there is a view that this friction was indeed insoluble and Britain would have found it impossible to placate both states.
Which view is correct?