The sign says “This signpost marks the 300th anniversary of the arrival of Alexander Selkirk (Robinson Crusoe) to Erith on October 14th 1711, his first port of call in England after leaving his island.” The sign points to Juan Fernandes Island, Chile, 7,750 miles away. The other arm points to Lower Largo in Scotland, Selkirk’s home at 460 miles away.
In September 1704, Selkirk was put ashore on the uninhabited Juan Fernández archipelago 420 miles off the coast of Chile as he had grave concerns about the seaworthiness of the vessel he was on, and wanted to make the necessary repairs before going any further. He declared that he would rather stay on Juan Fernández than continue in a dangerously leaky ship. He was taken up on the offer and was landed on the island with a musket, a hatchet, a knife, a cooking pot, a Bible, bedding and some clothes. After the ship had sailed away, Selkirk decided it was maybe not such a good idea but it was a bit late by then.
He was there for just under four and a half years before being rescued. Daniel Defoe published The Life and Surprising Adventures of Robinson Crusoe in 1719, which was based on the experience of Selkirk. The full and fascinating story can be seen at https://en.wikipedia.org/wiki/Alexander_Selkirk and https://www.smithsonianmag.com/history/the-real-robinson-crusoe-74877644/ and https://www.undiscoveredscotland.co.uk/usbiography/s/alexanderselkirk.html