But now Edinburgh Castle's original One O'clock Gun is to be heard across the city once more to mark the start of the Leith Festival.

It will be the first time the "18-pounder" gun has been used since the daily time signal was first established in Edinburgh back in 1861.

"Shannon the Cannon", the soldier who fires the Castle's larger guns before crowds of tourists every day, will even dress in period costume for the occasion.

The event will renew links between Leith and the famous one o'clock time signal, which was first established as a signal for sailors on the Firth of Forth.

The 18-pounder was donated by the Royal Artillery in Scotland, based at Leith Fort.

It was merchant seamen from the port who first synchronised the Castle guns with the timeball on Calton Hill, using a 4020ft long electric cable.

The city's master gunner, Sergeant Jamie Shannon, said he was delighted to be involved with the project.

He said: "It was the first One O'clock Gun to be successfully fired in Edinburgh and it's never been used again since the very early days, when it was replaced by the Dwarf Gun.

"It's good to be celebrating the links between the gun and Leith.

"Ritchie's the clockmaker and a lot of the people based in the original setting up [of the one o'clock signal] are all from Leith, and one of the main reasons for the gun was for the ship's captains on Leith Fort.

"It will be a good opportunity to promote the history of the One O'clock Gun again.

"A lot of people don't realise that the tradition has been going for 146 years and that it was originally one of these smaller guns that was used.

"It will be good for tourists that day as well, seeing it being fired from a different place from usual, especially with us dressed in the original uniforms. It should be a bit of a spectacle."

Because the gun has been sitting idle for so long, it is feared the barrel might explode if it was fired again.

Instead, pyrotechnics similar to those used when the giant Mons Meg gun is fired at Hogmanay will be brought into action.

Sgt Jamie Shannon will be dressed in the original gunner's uniform from the 1860s, including military shell jacket and original pillbox hat.

The uniform is being created specially for the occasion by a company called The Kit Bag.

The gunshot will be fired at the Castle's Half Moon Battery, looking out towards Leith, instead of the usual firing spot at the Mills Mount Battery, on condition that Historic Scotland gives final approval for the event.

Sandy Campbell, chairman of the Leith Festival Board, said: "It is fantastic for us that this will be happening, and it is more recognition of the fact that Edinburgh has more than one festival.

"It's also good to make the connection between Leith and the One O'clock Gun being set up."

He added: "People often forget the strong historical links that Leith has not just with Edinburgh but also with the rest of Scotland."

George Robinson, secretary of the One O'Clock Gun Association, said: "It should be a real occasion and it is another chance to promote the history of the gun."

THE FACTS

The idea was to offer an alternative to the crane ball at Calton Hill. The ball showed when it was one o'clock so that ships on the Firth of Forth could adjust their times and coordinates. But "Auld Reekie" Edinburgh was often very smoky and cloudy, so people had trouble seeing it.

That's where the gun came in. The time signal was sent from the Nelson Monument to the gun at the Castle via a 4020 ft-long overhead electric wire running across the city.

A team of merchant seamen from Leith were employed by clockmaker James Ritchie & Son to connect the cable between the Castle's time gun and the time ball at Nelson Monument, to ensure both went off at the same time.

The most famous gun at the castle is Mons Meg, a six-ton muzzle-loading cannon dating from 1457 capable of firing 150kg gunstones nearly two miles. It was last fired on October 14th, 1681, to celebrate James VII birthday, when the gun's barrel burst. It was taken to London in 1754 and returned to the city in 1829.