Buckingham Palace, the Queen's residence in the heart of London, may be surrounded by acres of the most perfectly manicured gardens, but its air has been revealed to be the most polluted in the country.
Grosvenor Place, which runs alongside the palace, has almost four times the maximum permissible amount of nitrogen dioxide.
The toxic gas is mainly produced from cars running on diesel, which is the fuel of choice for the thousands of London taxis that ply their trade in the centre of town. Increasing numbers of private cars in the UK now run on diesel as well.
The figures published by the UK's Department for Environment, Food and Rural Affairs show the average level of the gas was 152 micrograms per cubic metres of air.