Keith, you should then read Chapter 5 of Messinger, on Lord Bryce. Unfortunately the online scanned version goes little further than this, but from the titles I think the last four chapters should be interesting too.

In a different post you say that Macmillan holds Germany and Austria-Hungary responsible for the war. Point 1 - the lesser point is that Macmillan here is expressing her personal opinion based upon evidence which she and others have collected, and others are able to, and have, expressed different opinions. Whether or not they are historians is neither here nor there.

The more important point is that even if Germany and Austria Hungary were responsible for the war, it was still not necessary for Britain to fight it. The only reason was the preservation of the privileges of the elite.