Grimshaw bought a remote island called Moyenne in the Indian Ocean for £10,000, 50 years ago in his late thirties. The British man from Yorkshire was looking for a change from working as a newspaper editor in Africa.
When Grimshaw first bought the island, it was so overgrown with shrubbery that coconuts could not fall to the ground. Yet he transformed the hunk of waterless bush into a national park with a price tag of nearly $50 million, reported the National Post.
He said he bought the island while he was on a month-long vacation in the Seychelles Islands during the 1960s. A boy passing him by the street asked him if he wanted to buy an island.
He said his attempts to buy an island previously fell through, but after visiting Moyenne he knew immediately that it was the one. He struck a deal with the owners that day.
He enlisted the help of a local man, Rene Lafortune, to transform the island into a habitable place to live. Together they planted 16, 000 trees (including 70 mahogany trees) and built almost 3 miles of nature paths, which attracted birds and giant tortoises that now call the island home.
The island gradually taught me what to do...It knows itself what it wants, Grimshaw said.
The giant tortoise, though indigenous to the Seychelles, was hunted almost to extinction in the early 1900's.
Now 86, Grimshaw has 120 giant tortoises, 500 turtle doves, and various birds for company on the island.
He lives in a single story house with a message reading Please respect the tortoises. They are probably older than you.
Tourists are welcome to visit the island, where they can visit pirate graves, ancient ruins and go on a treasure dig, according to its tourism website. They can even have a bit to eat at the Jolly Roger Bar and Restaurant.
Tourist fees pay for the island's upkeep. Developers have expressed interest in buying the island, but Grimshaw said he has no intention of letting Moyenne be overtaken by multi-millionaires.
He said he believes only three other people have ever lived on the island.
Grimshaw spends his days taking care of the animals on the island. He says he keeps some of the baby tortoises in his bedroom because if you let them go, you'll never see them again.
Brendon is the modern Robinson Crusoe, said Joel Morgan, Seychelles' Minister of Home Affairs, Environment, Transport and Energy. He's a naturalist, he's a conservationist, and he's a damned hard worker.
Rumor has it that pirates buried $45 million in treasure on the island. Grimshaw said he has tried to locate it multiple times, but has thus far been unsuccessful.
Grimshaw will appear on 'Indian Ocean with Simon Reeve' on April 22 on BBC Two.