Addressing a London breakfast meeting of business people interested in Africa, the chairman of CDC, a private equity investor owned by the UK government, rolled out a biting anecdote this year.

“I was talking a few years ago to a finance minister in a south-east African country and emphasising the vital importance of reliable infrastructure in attracting foreign investors,” recalled Sir Malcolm Williamson. “Then the lights went out.” Knowing members of the audience chuckled wryly. Those operating in Tanzania would have winced.