The London 'Toxicity Charge' / 'T-charge' / Ultra-Low Emission Zone (ULEZ)

I support charging people who decided to drive in but think the pay-once-and-drive-all-day approach encourages exactly the wrong sort of driving.

True. However, road user charging by mile or some other measure can also have unintended consequences, e.g. suppose you're a tradesman who really does need a van to drive around all over London to wherever the jobs are (not that it's a business model I'd support, but it does exist, and not just for companies like Pimlico Plumbers, but also smaller companies and sole traders). You'll rack up huge bills. By contrast, you might be loaded and just driving your Lambo around for 'pleasure'--you'll probably be able to easily absorb the new cost. At least with the current model our little trader has some certainty about what they need to pay. Obviously, I'd love it if tradesmen were all able to switch to cargo bikes, but I'm sure there are some for whom that won't be possible. So, how do you organise it? Do you grant exceptions? Would everyone suddenly try to exploit loopholes that might open?

I'm also amused that Heidi Alexander's go-to example of what should be easy and free is a one mile car journey, when she spends the rest of her time encouraging people to do those journeys by bike or on foot.

I'm not sure she meant it like that, but rather that some people would have to dip into and out of the zone for a short distance when driving through Catford, quite possibly being on a longer journey. I'm sure the South Circular, as the relevant ring road, would remain exempt, as the Inner Ring Road is today, but it might be the case that some people couldn't stay on it all the way. Labour politicians do tend to be wary of regressive taxes, and in fact that was one argument many advanced when Livingstone did the original CCZ, and this £15 would be used by different people quite differently. Etc. Lots of different cases can probably be constructed that aren't very helpful, but I don't think she only meant to say that it would adversely affect people driving a single mile.

Technologically it's straightforward, but there's rather too much glossing over the practicalities and legalities. Will you need a tracker, or an app, and what happens if you have neither? Do the legal powers to make it happen exist, or does it need an act of parliament?

Yes, that's something that has paralysed the whole thing for a while--too many possibilities and options. Let's hope some kind of consensus emerges in the not-too-distant-future.