Clear skies help protect St Paul's

Clearer skies are helping to protect the cathedral from chemical erosion. Credit: Stephen Pond, PA.

The risk of chemical erosion to the stone facade of St Paul's Cathedral is at a 300-year low.

A recent study has found that the levels of sulphur dioxide - found in acid rain - have fallen by 95% over 30 years.

The drop is largely down to a decline in industry in central London and a move towards cleaner energy production, according to the report by the universities of Portsmouth, Oxford, Sussex and Cambridge.