Christopher Preece was killed in his kitchen, and the men left with just a few mobile phones and a small amount of cash, the Telegraph reported.
Preece's 56-year-old wife Felicity was also injured in the Saturday night attack, which happened on a farm the couple were turning into a nature reserve.
Preece's daughter-in-law said a gang of three robbers poisoned the couple's large pack of guard dogs before breaking into the house.
Preece, originally from Southgate in London, built his farm outside Ficksburg on South Africa's border with Lesotho.
His wife heard him crying for help, but was overpowered before she could call police. She sustained a fractured skull, the report said.
Since the country's first fully democratic elections in 1994, more than 3,000 white, mainly Afrikaans, farmers have been killed in their homes.
Police say the murders are normally carried out by drug-addicted, unemployed black men.
The attack at Preece's farm was the fifth such incident, and the second murder, in the district over the past month.
Preece had moved to South Africa in 1995 for work, after which he had "fallen in love" with the country. He worked as principal geotechnical engineer for a mining firm and was based in the country's commercial capital Johannesburg.
However he spent every weekend on the farm, where he wife lived.
London: In the latest in an alarming trend of brutal murders on remote farms in post-apartheid South Africa, a 54-year-old British engineer was hacked to death by three machete-wielding men on his farm, a media report said Monday.
First Published: Monday, November 26, 2012, 20:23