I wasn't the only person who thought the question setters had let themselves down with this question, which is the only one in the round that has a direct connection with the Prime Minister concerned.
The Gladstone bag was named by its inventor, leather goods dealer J. G. Beard, after the Prime Minister who was renowned for his love of travelling, and of whom Mr. Beard was a keen supporter. There doesn't seem to be any evidence that W. E. Gladstone ever actually used the artefact that was so named after him.
According to GladstoneBag.com (archived on the Wayback Machine), "suitcases as we know them today" evolved from the Gladstone bag.
(This site is cited by Wikipedia, and if I'm not mistaken it's the source of the description that's given in the question.)
© Macclesfield Quiz League 2018