Builders had a blast from the past this week when they unearthed what they thought could be a bomb in a Rochester garden.

But, after a closer inspection - and a game of catch - they discovered it was actually a cannonball from the 1700s.

The 12.2kg iron ball, buried 3ft in the ground, was dug up during excavation work in a garden at the back of a block of flats in Goddington Road.

The owner of one of the flats, 42-year-old Glen McConnel, said: "When the builder shouted that he might have found a bomb, I did rush out, but after we washed it down and had a game of throw and catch, we realised it wasn't."

The builder who uncovered the cannonball, who only gave his name as Jerry, said: "I was levelling out the ground and it came up in the bucket. I knew it was metal because it was rattling in the bucket and when I took it out I thought it was a bomb from either the Second World War or earlier."

Their excitement decreased after they discovered it was not a bomb and Mr McConnel considered whether or not to throw it in the skip or put it in as scrap iron.

After finding out when the ball was made, he said: "Now we know where it came from and from what era, we are really excited about discovering something so historical in the back garden. It's amazing to think that has been in the garden for that long.

"It also makes us wonder what else could be under there, but we will not be digging down any further as our new garages are being built."

A cannonball from the same period is on eBay listed for almost £500. Mr McConnel is hoping to donate the cannonball to a local museum, but says if no one wants it then he will use it as a doorstop.

Paul Evans, from the Royal Artillery Museum, in Woolwich, confirmed the cannonball dates back to the early industrial period.

He said: "Rochester is a good location to find cannonballs as the area has plenty of history. The British 12pr shot was in use for a very long time, roughly 1750 to 1860.

"Given the condition of it and the general poor production quality of it I would hazard it as being older rather than younger, industrialisation during and after the Napoleonic Wars meant they were much better quality."

Speculating as to how the cannonball got there, Mr Evans added: "It was either fired or dropped and left there. If it was being fired it could be from a practice round that had gone astray. It was just open ground then."

Stephen Nye, assistant curator, at the Guildhall Museum, Rochester, said: "Cannonballs were made from the 17th century onwards, until about the mid-19th century. Most found locally date from about 1780-1840.

"Because the Medway Towns have been the home of the Navy from Tudor times, many forts have been built - and most famously, the Chatham Lines - fortifications that provided a shield for the Dockyard.

"Consequently cannonballs, or round shot as they are called, do turn up frequently."