The Polo is not mine, I have the 4x4. S friend has the Polo.

Where I live it is law to have a fully functional catalytic converter and it's tested every year and replaced if needed.

Also it's a poor justification anyway, we don't legislate to fine people for something their car might be doing. But then that's not really what the congestion charge is aimed at because it's a really obvious poor tax that people tolerate because it will ultimately ease congestion, albeit unfairly.