The mass protest against a third runway at Heathrow Airport has been backed by the Archbishop of Canterbury.

Dr Rowan Williams will support the march on Heathrow this month, when thousands of campaigners are expected to demonstrate about expansion plans. He is planning to write a letter of support to be read out at the march.

But his stance goes against the Government's views. Prime Minister Gordon Brown has called the expansion of the airport "desirable".

A decision about whether to create a third runway, sixth terminal and a huge increase in flights is expected to be announced soon.