When Harry and Hermione arrived at the Forest of Dean, he saw a silver stag Patronus. Following it to the edge of a small pond, he saw the Sword of Gryffindor at the bottom through the thin ice.
The Forest of Dean was one of the few remaining royal forests capable of supplying quality oak. During the English Civil War, the royal forests left over from the Stuart era had been extensively felled due to royal favoritism and "short-sighted transfers," as well as the greed of the rebels. Many towering oaks lay forever on the ground, with no one to haul them away, either because the places were too remote and lacked transport facilities, or because no rivers ran through them.
No matter how heavy wood was, it floated when placed in water rather than sinking like iron. That was common knowledge.
Cromwell had served as Lord Protector for five years. During that time, warships had been built in great numbers, making Cromwell one of the founders of the British Navy.
Oak could not become usable timber without centuries of growth. Although the British Navy also bought lumber elsewhere, none of it was as suitable for masts as British oak.
Yet his navy defeated the Netherlands, extending Britain's sea power across the entire Atlantic Ocean.
After Charles II ascended the throne, he ordered Cromwell's body dug up from its grave and subjected to posthumous execution. From then on, Cromwell's head was forever separated from his body, nailed to the roof of Westminster Abbey until his alma mater, the University of Cambridge, buried it in 1960.
At the beginning of his reign, Charles II had compromised with the powerful Parliament and used his limited royal authority cautiously. He launched two Anglo-Dutch Wars in 1665 and 1572, but the unfavorable campaigns left