China's most outspoken billionaire has gone silent. No one has seen Jack Ma at the business school he founded. Nor at his tai chi studio. His raucous speeches headlining an annual meeting of entrepreneurs in his home province of Zhejiang have been put on hold.

Since Chinese President Xi Jinping unexpectedly called off the blockbuster public offering of Ant Group, Mr Ma's payments and lending business, five months ago, Mr Ma has made a single public appearance.