Doctor Who beautifully connects the current era to William Hartnell's First Doctor, adding a finishing touch to the classic story "The War Machines." Doctor Who: Flux continues with "Survivors of the Flux," which takes a surprising detour through UNIT history, forever changing the organization's origin as we know it. The mysterious Grand Serpent time travels to 1958 and infiltrates UNIT during its inception, manipulating (and ultimately killing via creepy alien snake) original founder, General Farquhar.
Doctor Who: Flux's UNIT rewrite respectfully salutes Nicholas Courtney's Brigadier Lethbridge-Stewart, and offers a taste of how the British authorities viewed extra-terrestrial activity when The Doctor's antics were only just beginning. There's even a reference to one of the First Doctor's earliest adventures - "The War Machines." As Farquhar and the undercover Grand Serpent descend the staircase at UNIT headquarters, the General bemoans, "We missed the whole thing at the Post Office Tower."
Set in 1966, Doctor Who's "The War Machines" draws upon the real-world construction of London's Post Office Tower. William Hartnell investigates a brand new supercomputer called WOTAN being programmed at the site, and discovers the machine secretly plans to - and this was fairly original in its time - destroy the inferior human race using an army of machines. Though it's obviously The Doctor who saves the day, WOTAN's War Machines do battle with the British military in the middle of England's capital city. UNIT wasn't conceived at this point, but "The War Machines" proved a fictional Earth-based counter-alien force could work in Doctor Who's future, paving the way for UNIT's introduction 2 years later.
Doctor Who: Flux's "thing at the Post Office Tower" line finishes off the original First Doctor adventure nicely. The "Survivors of the Flux" UNIT scene takes place in 1967, one year on from "The War Machines," and it's clear the incident remains fresh in Britain's memory - as it should, given the scale of the military vs. machine battle that transpired. In Doctor Who's book of Earth history, major invasions and events are often forgotten without explanation, never to be mentioned again. Hearing General Farquhar mention WOTAN in "Survivors of the Flux" underlines the importance of that chapter in the First Doctor's journey.
Farquhar is clearly disappointed UNIT missed out of the War Machine festivities, but the General perhaps shouldn't be too hard on himself... after all, UNIT arguably shouldn't exist in 1967. The organization's first appearance came in the 1970s-set Second Doctor episode "The Invasion," where a newly-promoted Brigadier strongly suggests his task force has only been recently established. Whether this is a glaring plot hole or the Grand Serpent's meddling at work remains to be seen, but if UNIT did exist in the First Doctor era and didn't bother showing up at Post Office Tower, that's a jolly poor show from the chaps in berets.
By referencing the First Doctor's adventures directly, Doctor Who: Flux also draws a line between William Hartnell and Division. If UNIT failed to help out against WOTAN, the Grand Serpent might've been responsible. Though his purposes remain unclear, the villain is likely connected to The Doctor's past and the Timeless Child. And if the Grand Serpent was meddling in the First Doctor's affairs from the shadows, that means Division was already catching up - even if The Doctor himself wasn't aware of it.