Why Boris Johnson is against third Heathrow runway

It is almost two years since Boris Johnson published a document calling for a new airport for London and he has consistently maintained his position since.

In his foreword to the January 2011 publication, Mr Johnson said Heathrow was "not the answer" and that Britain had failed to act on aviation.

He also said that Britain had been "paralysed by the difficulties surrounding aviation rather than recognising the opportunities".