An enormous 50% of the funding for London's new air ambulance came from the secretive society of Freemasons, it has emerged.

A sum of £2m ($3.1m) has been offered to pay for a second helicopter in the capital's sky by the Freemasons.

London is the location of global Freemasonry's headquarters - the imposing Freemasons' Hall near Covent Garden, in the heart of the city.

There are reportedly around 40,000 Freemasons in London and male-only members are united by a hushed code and arcane rituals for mutual advancement. The society claims it is non-political.

The air ambulance is not part of the NHS and so relies upon charity donations to operate. The Freemasons were hailed by the chief executive of the charity which operates the helicopter service.

"We have now crossed the halfway mark for the Your London, Your Helicopter campaign, thank you to all those who have helped us get there," said Graham Hodgkin.