Navigating Chinese stock markets? Pack motion-sickness pills. Intraday swings of more than 5 per cent have become common; in the past two months, mainland indices have had intraday movements of more than10 per cent three times. Chinese authorities have been stepping in to prop up shares. One can only assume this is making the turbulence worse.

State protection, if that is the word, has not extended to the Hong Kong bourse. Shares there have trickled persistently lower, without the churning volatility. Shanghai’s composite index is still up nearly a fifth this year. Hong Kong-listed Chinese ‘H’ shares are down more than 10 per cent.

For the nearly 70 companies listed in both Hong Kong and China — names such as China Construction Bank, China Railway Group and Tsingtao Brewery — the Hong Kong H line is on average 24 per cent cheaper than the same ‘A’ share bought in China. That is less than July’s one-third discount, but well above the five-year average.