S.O.S.

"...Eventually the conference plumped for - dot-dot-dot, dash-dash-dash, dot-dot-dot - a signal that is hard to mistake for anything else in the world of morse.

"SOS is very simple you are not going to hear that at any other time," Mr Eavis says.

But it needn't have been SOS of course. Being broadcast without a pause, the combination of dots and dashes could also have been read as IJS, SMB, or VTB. SOS won the day, coming into effect on 1 July 1908.

Since then it has stormed into popular culture, littered a thousand newspaper headlines and prompted numerous "backronyms". According to who you believed it was Save Our Souls, or Sinking Of Ship, or Send Out Succour or Save Our Ship.

"None of which is correct," says Mr Eavis. "It doesn't stand for anything. It's simply non-stop, there are no spaces."

It is believed the first ship to have sent out an SOS signal was the American steamer Arapahoe in 1909. When the Titanic was sinking in 1912, its operator first sent out CQD and then SOS, alternating. CQD persisted, particularly among British operators, for many years...."