cofty, what an interesting article that is. One other factor which is barely touched on in the article but which I think may well be central to Darwin's concessions to people of faith, is the fact that his wife, Emma, who he had known all his life and to whom he was devoted, was a very devout believer. He knew of the concerns she had about the work he was doing and no doubt did not want to cause her any pain while still remaining true to his convictions.
I cannot help myself but to tease you with the conclusion of the article:
He could still find it inconceivable that the universe was the result of chance alone. But – and with Darwin there is so often a nuance - if the human mind was itself the product of evolution, what confidence could one place in any metaphysical or theological conviction - even one’s own?