The more money an investor has, the more frequent their errors. Thus theorised tycoon Jack Ma last week. Who could he possibly have been referring to? Masayoshi Son was on the same conference panel. News that Mr Son’s SoftBank is selling a big stake in overhyped US dog-walking start-up Wag shows Mr Ma has a point.

Implicit criticism from the founder of Alibaba must be painful, even for the brash Mr Son. A big shareholding in the Chinese ecommerce group is the main asset of his Tokyo-listed tech investment group. Writedowns on flops such as Wag make fundraising for a second tech-focused Vision Fund harder. Selling shares in Alibaba must be tempting for Mr Son. But that would badly damage SoftBank’s share price.

SoftBank has agreed to sell its nearly 50 per cent shareholding in Wag back to the company. It is expected to lose money on its initial investment, made when the loss-making business was valued at $650m. SoftBank has missed its chance to cash out on another investment, OneConnect Financial Technology. This filed for a US listing last week at a valuation up to $2.7bn lower than when SoftBank invested. The net loss of the Chinese cloud fintech start-up widened to $147m in the first nine months.