Implying that whatever London does about air pollution, there will still be a high level unless other areas control car usage etc.
(Note that London is in a “dip” and that pollution can settle for many days over London depending on the weather. For people outside of the UK, we often think of London as being everything inside of the M25, but it is not well defined what “London” means.)
It's really hard to vet an article when the only reference is to a study located behind a paywall.
The only facts the article presents include:
12 million people who live outside London produced 77 per cent of the region's emmissions.
Those 12 million drove an average of 15.6 miles
The 8 million in London produced 23 per cent of the region's emissions
Those 8 million drove an average of 7.7 miles
I don't see support for your conclusion because the article doesn't say what percentage of the air problems are limited to London only. Which means we can't make any conclusions with regards to what will happen to London's air based on London's pollution controls. We also can't make any conclusions as to what will happen to London's air with regards to pollution controls on areas outside the city.
Once you look at these numbers a bit something interesting does pop up. The amount of emissions assigned to the two areas (in and outside London) are very close to the division of number of miles driven. People inside London drove 25% of the total miles vs 75% for people outside London.
I'd think that the variation on emissions here would be quite a bit wider (and in the opposite direction) given that people inside London tend to be in highly congested traffic more often than those outside. In other words a single mile driven in London should net a much higher level of emissions vs a single mile driven outside London. Then, again, the facts presented don't tell us where those miles where actually driven nor how they arrived at the percentage breakdown of responsibility for regional emissions.
I'm not from the area so I don't know how common it is for people outside London to drive into London and vice versa. If it is like most major cities then a fair amount of people that work in London actually live outside it; which would suggest that a large part of the problem can be resolved by London itself.
To be quite frank, what I see is an article trying to limit fallout from emissions targets not being met and obfuscating blame without giving the details necessary to support the reasoning.