Final answer:
Elizabeth I did not formally designate an heir, but James VI of Scotland succeeded her as he was the closest living male Protestant relative, being the son of Mary, Queen of Scots.
Step-by-step explanation:
James VI of Scotland inherited the English throne upon the death of Elizabeth I, who passed away in 1603 without an heir. This claim was mainly because James was the nearest living male relative, namely the first cousin of Elizabeth through his mother, Mary, Queen of Scots, who was Elizabeth's aunt. It is important to note that there was no formal declaration by Elizabeth I naming James as her heir, but he was widely recognized as the most likely successor due to his blood relation and the Protestant faith needed to ascend to the English throne.