Jim, even you can not deny that the Times Higher Education Supplement reviewer did read Pennell's book.

He says she argues, "that the public's support for war against Germany was based on a reluctant, but rational, agreement that it was necessary. After an exhaustive search in primary sources, she concludes that "in reality, the responses of ordinary British and Irish people were much more complex than the myth of war enthusiasm would suggest...[they] did not back the war because they were deluded, brain-washed and naively duped into an idiotic bloodbath, as the subsequent myth would have it"."

Another direct quote from the book, "the majority of people - including those in Ireland - supported the onset of war in a spirit of seriousness and acceptance of duty".

"That support for the war was no late-summer madness, born of a foolish optimism and the expectation of early victory, is demonstrated by recruiting figures. "

" It is significant that it was in September 1914, after the retreat from Mons and the revelation in The Times of 25 August of just how hard-pressed British forces were, rather than in the first weeks of war, that the greatest number of recruits came forward. As it became clear from military reverses that there was little hope of a swift and glorious end to the war, and as reports of German atrocities in Belgium circulated, so resolve hardened. This was no "war fever", but a commitment to victory by a UK convinced of the justice of its cause."

"the concept of popular support as an irrational fit is demolished convincingly by Pennell. Historical myths are notoriously enduring, but that of a British "collective war enthusiasm" at the outbreak of war in 1914 should not survive after this excellent and important book, and should be replaced by a view of a nation accepting the need for a war of national defence."
https://www.timeshighereducation.com/books/a-kingdom-united-popular-responses-to-the-outbreak-of-the-first-world-war-in-britain-and-ireland/420302.article