Killing us while protecting us

The pedestrian on Camberwell New Road was holding her nose to try to block out the smell and pollution from someone burning tyres or similar. At least, that what I thought the smell might be as it hit me. It turned out to be the totally foul exhaust from the army truck pictured - worse than the average black cab by a huge factor.

Army Driver, Be the Best says the advert on the back.

What are the odds the army are exempt from the rules of a Low Emissions Zone?