Thomas Markle believes he can be a target for criminal gangs after publicity about his comments about his daughter Meghan and her husband, Prince Harry.
The 74-year-old has revealed to a confidant that he is now a & # 39; sitting duck & # 39; feels at the dilapidated resort of San Antonio Del Mar, where he has a modest guest house on the hilltop.
It is only 13 miles south of the lawless border town of Tijuana, a stronghold for a drug cartel where more than 1,700 murders were registered last year.
Markle was also ruthlessly chased by the paparazzi and his friend confirmed: "He fears the prospect of constantly looking over his shoulder for the rest of his life.
"Thomas is a heart patient who is supposed to create a stress-free environment for himself, but the truth is that he is almost constantly anxious and leads a seminomadic existence."
Markle, who last month pleaded for a "last chance" to make peace with newlyweds Meghan and Prince Harry, has spent little time at home since missing their royal wedding in May to undergo heart surgery.
Instead, he hid for a while with friends a few miles away in the more luxurious coastal town of Rosarito, where much of the film Titanic was filmed, according to his confidant.
He also stayed in a series of motels on both sides of the Mexican border and watched Windsor Castle wedding on TV in a hotel along the road in San Diego when he recovered from his operation.
Our source added: "He has replaced all locks at home for a much more refined set-up.
& # 39; He has done everything to increase security, but he is stuck there because he can not afford. He still does not feel safe and fears that his location turns him into a sitting duck. & # 39;
The latest travel advice for the US Department of State Department states: "Violent crime, such as murder, kidnapping and theft is widespread."
And it warns that even ex-pats like Markle are almost certainly left to their fate, and added: "The US government has limited opportunities to provide emergency services in many areas of Mexico."