At first, gardener George Harris thought the rancid bottle he unearthed in a museum flower bed had been left by a litter lout.

It was caked in mud and smelled musty but he was surprised to dig it up intact so took it to show a curator instead of dumping it.

The discovery turned out to be a rare antique wine bottle, which probably dates back 259 years.

Experts at Preston Manor in Preston Park, Brighton, said the bottle was one of the most important artefacts they had ever found and believed it could reveal a secret history about the activities of a past owner.

The bottle has aged with a scaly surface but hardly any scratches. It will be cleaned and conserved before being put on display in the manor.

Once the bottle was dusted off, it revealed an inscription that reads T Weston 1742. Thomas Weston owned Preston Manor at the time and had it rebuilt four years earlier.

Mr Harris, the garden manager, was one of a team carrying out restoration work to the walled garden of the manor.

He said: "I can't believe it wasn't smashed beforehand because we've just had a mini-digger in to churn up the ground before re-laying the path and I found it right on the edge of the path.

"It's unbelievable to think it has been sitting there for more than 200 years, especially with all the changes to this patch of ground during the years.

"It just amuses me that I carried it into the manor like any other old, discarded bottle, by the neck and swinging it, but when the curator brought it back down he was gripping it with both hands and carrying it like it was the holy grail."

When the experts tested the bottle they discovered at least one interesting conundrum - a residue found inside it is thought to be age-old urine.

Mr Harris, 49, of Queensway, Brighton, said: "We have joked that Thomas Weston snook out into the garden and drank the bottle dry before relieving himself."

Preston Manor keeper David Beevers said: "The fact this bottle is completely intact makes it a most remarkable find. It is the oldest artefact we have directly connected with the manor."