The bane of raw intelligence – and history – is that you can always look back and find the signs, but you can’t necessarily look ahead and see where they’re pointing. Many questions remain about the intelligence failures that enabled an insurrectionist mob to lay siege virtually unimpeded to the US Capitol. But here’s one sign that’s been flashing in my head since 6 January 2021. Four days before the 2020 election, a “Trump Train” of motorists swarmed a Biden-Harris campaign bus on Interstate 35 between San Antonio and Austin. Kamala Harris would have been on the bus but for...