Years of neglect, corruption and mismanagement at Eskom under the country's African National Congress (ANC) government have seen it fall from a utility once lauded as the best in the world, to one that cannot keep the lights on.

Prof Mamphweli said: “We have coal power stations that were not properly maintained and there was quite a lot of neglect and that's catching up with us.”

Eskom's ageing 15-strong fleet of coal-fired power stations provide the great bulk of the country's power, but has suffered years of deterioration.

As the ANC government has delayed or bungled programmes to procure more capacity, the existing fleet has been run into the ground. Meanwhile, the utility was alleged to have been systematically looted during the rule of former President Jacob Zuma and today's executives admit corruption persists. Eskom remains heavily in debt, with nearly £2.5bn in unpaid bills owed by South African municipalities alone.

The result has been frequent breakdowns that take longer and longer to repair and rolling blackouts to protect the grid. Engineers at the utility say they have had their worst weeks in recent memory, suffering 90 breakdowns between September 3 and 18.

As blackouts have mounted, the knock-on effects have spread through the economy. Some mining firms say they have cut back smelting operations to prioritise power for mining operations.

Mobile phone networks have warned their services may fail. Vodacom this week warned the battery back-ups on its cell phone base towers do not have enough time to recharge fully between blackouts. 

“These have limited power and will eventually fail,” the operator said. Main rival MTN says it is burning through more than 400,000 litres of fuel each month to keep 2,000 generators running.

Small retailers without back-up are particularly being hammered. Cashiers' point-of-sale card machines are packing up during blackouts, leading frustrated shoppers to abandon shopping trolleys when the lights go out, as they cannot pay.

“South Africa’s growth potential continues to diminish” every day that the power cuts continue, economists at Rand Merchant Bank said.

“The outlook remains one of more pain to come as South Africa assets are fragile and prone to weakness in an environment of deteriorating fundamentals.”

Energy experts warned as far back as the mid-1990s that the country risked running out of power, but nothing was done. Load-shedding began in 2007 and has since got worse. 

Eskom has said it intends to start signing deals this week to buy 1,000MW of additional power.

In July, after that month's bout of stage-6 blackouts, Mr Ramaphosa unveiled what he said was a power plan “to achieve long-term energy security and end load shedding for good”.

That involved attracting more private investment, speeding up the procurement of more generating capacity and fixing existing power stations.

As he arrived back to deal with the problem, he vowed the government would “remain seized with this issue until the situation is resolved”.

“The severe load shedding of the last few days has reminded us how unstable our ageing power stations are,” he said.