Some key bits:
By 1500, the sweet potato had become an established crop in western Europe. “Common,” or white potatoes, took a bit longer to catch on; they arrived in Europe as a cultivable vegetable between 1550-1570.
Britain was one of the last European countries to take to the potato; the first mention of potatoes (sweet or otherwise) in a printed British book was in 1596, when famed herbalist and botanist John Gerard included it in his Catalogue. This was apparently so well-received that a year later, Gerard devoted an entire chapter of his famous 1597 Herbal to this new and unfamiliar plant.
Which reminded me that the Herball often has brief explanations of how to eat the items listed. So off I went to the original.