Diesel cars: 'It turns out we were wrong'
Sadiq Khan is announcing plans to speed up tougher rules on vehicle pollution in London.
Diesel cars will face the highest penalties for driving in the capital.
The number of diesel cars in the capital has gone up in recent years despite tests finding they are incredibly damaging to public health.
Sir David King, the Government’s special representative for climate change and the chief scientific adviser under both Tony Blair and Gordon Brown, told the Today programme the Government was wrong to encourage diesel vehicles.