Until last week, Tsai Ming-kai, the Taiwanese billionaire once known as China’s “bandit phone” king, was on a roll.

The founder and chairman of chip design house MediaTek had already seen his personal wealth jump by 80 per cent last year. The launch of the company’s “Dimensity” chipset for 5G smartphones and Washington’s blacklisting of Chinese technology group Huawei from buying from US chipmakers had sent MediaTek’s shares soaring.

This year, things looked even brighter. The US in May barred chip manufacturers from selling to Huawei any custom-made semiconductors produced with US equipment. For Huawei, the most obvious solution was MediaTek’s off-the-shelf smartphone chipsets, a development that would have boosted the Taiwanese company’s fortunes immensely.