That was Colin Fletcher, author of 'The Complete Walker' and the follow up books like "The Complete Walker 2' and so on. He talks about his 6 inch fixed blade he carried in book one, but by book two he had ditched the fixed bade as it was never used, and he'd bought the little SAK. He never used the nail file blade so considered cutting it off.
Fletcher was quite the accepted expert on backpacking, and did the solo hike the length of the Grand Canyon and some other pretty epic trips. He had quite a bit of knowledge of outdoor survival from him being a British Commando in WW2, and living off the land when parachuted into hostile territory.