James Starkey invited his killer in.

So says the general manager of the luxury apartment block in Johannesburg where Mr Starkey, an Australian banking consultant, was found dead in his room last month.

"This incident was not a breach of security in the building and took place between the tenant and his invited guest in a private apartment," Legacy Hotels' David Stroud said.

"We are not in the habit of presuming to tell occupants who they should or should not have visit them."

Mr Starkey had been nearing the end of his three-month project working in Johannesburg for London-based banking consultancy Catalyst.

His body was discovered on October 8 in the Raphael Penthouse Suites, owned by Legacy Hotels, after a concerned colleague asked staff to check on him.

The body bore burn marks and signs of strangulation, a paramedic told another financial services worker.

Mr Stroud said staff had to ask apartment tenants for permission to let visitors enter.

"While we have biometric readers and security personnel present 24/7, and we can control what takes place in the common areas, we have very little control over what takes place in private and behind closed doors," Mr Stroud said.

While the entrance was captured by CCTV, South African police say they have no motive and no suspect.

Police spokesman Lungelo Dlamini has confirmed the case is being treated as a murder but would not comment on injuries.

"Words cannot describe how devastated we are," Mr Starkey's family said in a statement released on Monday.

"James lived life to the full and certainly had everything to live for, having recently become engaged and planning to return to settle in Australia in the near future."

Mr Starkey worked for a variety of financial services firms including Goldman Sachs, Macquarie Bank, Ernst and Young and JP Morgan, first in Australia and more recently London.

A spokeswoman for his most recent employer, Catalyst, said: "We are deeply distressed and offer our most profound condolences to his family."

Britain has taken the lead in providing consular support to the family, as Mr Starkey was a dual-national who entered South Africa on his British passport.

But Britain's Foreign and Commonwealth Office said the country did not have jurisdiction to investigate the killing.

Mr Starkey's family said: "For now, we are trying to stay focused on supporting the investigation by the South African Police Service to find justice for James."

His body was repatriated to Sydney and buried in Macquarie Park cemetery on October 21.