Heritage architect Henry Paine described the burning of the old Rissik Street Post Office as an "unspeakable" shame.
"I don't know what to say. I'm equally furious and despondent," he said, adding that officials at the City of Joburg Property Company (JPC) should be held accountable for the loss and immediately charged.
"This is not something they didn't know about. The clock was stolen 10 years ago - and the bell in the clock was an actual replica of the small bell in Big Ben. There has been a gradual dismantling of the building over 10 years," Paine said.
Cast iron columns in the building had also been stolen. "Those columns would have needed 20 men to shift one. And still the JPC couldn't stop them."