Dig in behind it and you'll find that the gold standard was abolished by the Currency and Bank Notes Act of 1914 resulting in the printing presses being fired up and fiat currency rolling off.
Not getting into politics here, this is a question of accuracy. Text of the Act does not say that.
"Be it enacted by the King’s most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal, and Commons, in this present Parliament assembled, and by the authority of the same, as follows:—
1.— (1) The Treasury may, subject to the provisions of this Act, issue currency notes for one pound and for ten shillings, and those notes shall be current in the United Kingdom in the same manner and to the same extent and as fully as sovereigns and half-sovereigns are current and shall be legal tender in the United Kingdom for the payment of any amount.
(2) Currency notes under this Act shall be in such form and of such design and printed from such plate and on such paper and be authenticated in such manner as may be directed by the Treasury.
(3)
The holder of a currency note shall be entitled to obtain on demand during office hours at the Bank of England payment for the note at its face value in gold coin, which is for the time being legal tender in the United Kingdom. ..."
(emphasis added)
With due respect, the act as written establishes what amount to gold certificates, redeemable in gold. Whether or not the government cheated and used it as fiat currency, printing more notes than they had gold in the expectation that most people wouldn't redeem them, I don't know. Whether the use of paper in lieu of a gold coin weakened the gold standard, I don't know. That seems to be the assertion of the site that hosts the text of the act, but I'm not an expert on currency and I'm not about to explore the details of the Brit WW-I currency system in a Trav forum. However, the act as worded clearly did not abolish the gold standard, and the fact that war had literally just been declared makes it difficult to say whether any later inflation was related to this Act or to other wartime economic factors.
https://www.gold.org/sites/default/files/documents/1914aug6.pdf
Of more interest to me from a Trav perspective is the increase in costs of goods that seems to generally accompany a war. Britain in that two-year period was dealing with the German effort to squeeze off her maritime trade with submarines. Trav worlds range from worlds with populations smaller than a Brit town to worlds as densely populated and economically diverse as Earth. It is conceivable that many of these worlds would experience economic disruption in wartime as worlds were besieged, commerce raiders prowled, resources and goods were diverted to wartime needs, local communities dealt with the loss of customers as troops and sailors headed off to other worlds to meet the enemy, and so on, and so on. What's less clear - because only GURPS gives a detailed picture of interstellar traffic and because we can only make educated guesses about the other factors - is the degree of disruption that would occur. Given the tremendous variability between worlds, I suspect we're pretty free to paint the picture we want on that score, within a broad range.