A 1969 camera operators' strike created Upstairs Downstairs multiverse

That's a great example of the same kind of accidental branching timeline

NTSC's problems versus PAL is more of a first-mover problem. NTSC was standardized a decade before PAL so the technology wasn't as advanced, and the PAL authors got to see NTSC get implemented. But by the time PAL was implemented NTSC was already entrenched in North America and some other markets and PAL's superiority wasn't sufficient to get people to abandon the older standard.

I'm no expert on cameras, but this seems to explain it:

https://en.wikipedia.org/wiki/Four-tube_television_camera

This says the main reason for four-tube is image registration. Basically, the incoming light is optically split up into red, green, and blue, and these go to separate sensors. Being separate sensors, they may not be physically aligned. So if you sum R + G + B together to get luminance, the picture will not be sharp.

You can solve this by adding a fourth (black and white) tube for luminance. Since it's just one tube, there is no alignment issue for the luminance part of the picture. And the eye is less sensitive to color, so while the color alignment issues remain, they aren't very noticeable.

At first when I read this, I assume the camera must have to somehow combine the fourth tube's signal with the other three tubes' signals. But since both NTSC and PAL encode luminance and chrominance separately, apparently this isn't necessary. It's the TV that combines them. With a three-tube camera, the sensor signals have to be split into luminance and chrominance. With a four-tube camera, you just take luminance from one sensor and chrominance from the other three sensors.

Not really, pa will show up fine on a black and white tv, as the chroma is lost in the line blanking. Some very poor b+w tvs with terrible filters might show a little high frequency noise but that’s it.

The big difference in the U.K. is that 405 lines was on vhf channels. The move to colour was also a move to pal, 625 and uhf.

625 lime receivers came out in the early 60s, and typically would also work with 525. Bbc 2 launched on 625 in black and white in 1964 I think, but didn’t add colour until 1967. 405 only sets stopped being sold by the end of the 60s.

Only bbc1 and itv transmitted 405, but continued until the 1980s. Most 625 sets were black and white 625 lines, and that slowly changed during the 70s.

A 625 black and white set from 1965 could pick up tv signals and display them fine (in b&w) until analog switch off around 2010 (phased across the country. The final 405 lines worked for 20 years.

Like ntsc colour was a sub carrier which exposed the colour difference signals. Unlike ntsc, pal switched the Phase on Alternate Lines, so reflections and other signal interference canceled out, like it does with balanced audio (and indeed balanced data in cat5 cables). NTSC didn’t have this correction so sets had a “tint” control to adjust the signal.

This led to the moniker “never twice the same color” for ntsc.

AFAIK no - in both NTSC and PAL you're transmitting a monochrome signal plus some extra analog information that encodes two additional color channels. The difference between NTSC and PAL is primarily the framerate and the color encoding method: PAL encodes color in a slightly different way (by Alternating the Phase on each Line) that's more robust to analog distortion. But it's still ultimately encoded as a color subcarrier on top of a black-and-white signal. The only relevance the 4-tube cameras have to the story is that they provided an easy and convenient way for striking camera operators to kill color.

The big sin in NTSC is the 59.94fps field rate. This is because NTSC transmitted on 6MHz channels that were fully utilized, there was no space for color. A naive implementation of this at 60hz field rate would mean beat frequencies with the audio carrier, giving visible dot patterns in the signal. Slowing down the field rate got rid of that interference.

PAL was based off an existing German 625-line system that was transmitted on wider channels, so they had extra bandwidth. No slowdown was required. But at the same time PAL was not a clean break, nor was it British. It's a German standard that applies the same general idea as NTSC[0] to German B&W. It was only a clean break in that didn't use the UK or French systems[1], which were either too low or too high resolution to be practical for 1960s color tubes.

[0] If you want to see a real sin, go take a look at the alternate history of interlaced-color TV that NTSC saved us from. NTSC is a sin in the same way that putting the Red Cross logo on a health pack in a videogame is technically a war crime.

[1] Which, to be clear, also had enough bandwidth for color without a beat frequency.

Early color TV is one of those topics where every answer seems to open three more trapdoors

British TV in that era was enormously, shall we say, frugal. As soon as they discovered videotape, which was both cheaper than film and reusable, they went all in on it. BBC especially (and ITV as well, it appears) often wiped their tapes and recorded over them to save money, since they saw no reason to think anyone would be interested in their shows in the future. For this reason, some early episodes of Doctor Who are lost forever, at least until some foreign TV station finds copies in their vaults, which has happened over the years.

That is effectively what Uber did. Internet and GPS make taxi companies and “Knowledge” unneeded for taxi drivers. This destroyed local (badly run) monopolies, but also job security for taxi drivers.

This is basically the entire story of the Industrial Revolution.

This never doesn't happen when capital holders control the economy.