On the sprawling maizefields outside Johannesburg, the Engelbrecht family knows the full horror of the farm attacks that are so commonplace they no longer rate a headline.Last Mother's Day Jo-an Engelbrecht was expecting his elderly father and mother for lunch. When they failed to appear, he walked up to their house."They were tied. My dad was lying on his back, my mother was lying face down. Their throats were slit, they were tortured," he says. The killers had extracted the keys to their safes and cars."My dad knew it was coming. We all know it's coming. It's just a question of when," says Jo-an.The old couple were duly added to the tally of farm murders that some Afrikaners believe are part of a wider political campaign to drive them off the land. While the numbers – some say 47 last year, others say 84 – are in dispute, there's no argument that the crimes are horrifying.But as Jonathan Holmes reports, they pale beside the nearly 20,000 South Africans, black and white, who were murdered in 2017 alone.In this confronting report, Holmes asks whether the killing of white farmers is just a tragic fact of life, and death, in one of the world's most violent societies - or whether it is indeed politically or racially motivated.The siege mentality of white farmers is magnified by radical politicians like Julius Malema. His Economic Freedom Fighters party sprang from the country's chronic failure to deliver land to landless blacks."We are taking the future into our own hands," he tells a rally of dancing followers in their red berets. Then a chant: "Shoot to kill! Shoot to kill! Pow, pow!" as he pulls an imaginary trigger.Recently Malema wedged the governing ANC into supporting expropriation of land without compensation. So far, the government has not seized any farmland without paying for it.But white farmers say that already the private market for farmland has collapsed. "Why would you buy a farm if tomorrow the government is going to take it?" asks Jo-an Engelbrecht.For now, Engelbrecht is digging in on his farm in the faint hope that President Cyril Ramaphosa can stabilise a country wracked by crime and corruption after a decade of Jacob Zuma's rule. But for his daughter Tessa, her grandparents' murder was the final straw. She wants out – maybe to Australia, if those hints of fast track visas materialise. "I wouldn't think twice if I got the chance," she says.