Broadcom’s $142bn (£104bn) pursuit of Qualcomm was always set to be risky. Competition regulators, stubborn management, and the disapproval of shareholders were all good reasons for its mammoth offer for the US semiconductor giant - what would have been the tech industry's biggest ever deal - to struggle. Few counted on Donald Trump delivering the killer blow, however.

The exchanges between Singapore-based Broadcom and its American target in recent weeks have resembled a soap opera as discussion dragged on and turned increasingly hostile.

But it all appeared to end quickly, with one swoop of the president’s pen on Monday night. Blocking the proposed deal on security grounds, Trump’s order said that “Broadcom … through exercising control of Qualcomm, might take action that threatens to impair the national security of the United States”.

Even for the unpredictable Trump administration it was a shock move. Not only are presidential orders blocking bids for national security reasons exceedingly unusual, but Hock Tan, Broadcom’s chief executive, appeared to be on solid terms with Trump.

Only five months ago, the two held a televised press conference in the Oval Office announcing that Broadcom, which is best known for microchips that process Wi-Fi and Bluetooth signals, would be moving its base from Singapore to the US, earning two separate congratulatory tweets from the president.