The couple, who bought the house and garden in Roanne in 2002, first discovered six gold bars in the garden in 2009, and a further 22 in 2013.

They maintain that they found them by accident both times, and had legally declared their discovery to the police, the Mayor’s office, and the Banque de France.

Yet, the couple became the subject of a criminal investigation by the prosecutor’s office in Roanne, after “atypical financial operations” were noticed.

It later transpired that they had sold 23 of the 28 ingots and pocketed the money.

When the previous owners of the house - the seller’s widow, and their eight children - learned of the discovery, they sued the couple for damages and compensation, claiming that they rightfully owned the gold, as former owners of the property.

The case centred on the 28 gold ingots, with a total value of almost €800,000.

Lawyer for the couple, Me Hugues Romeau, said: "Everyone had told them that the ingots were theirs...In good faith, they considered themselves the owners of the gold."

Yet, in 2015, the court ruled that the previous owners had offered “sufficient proof” of their rightful ownership of the gold.

It ordered the discoverers to return the remaining ingots, along with the money from the sale of 15 of them.

Having been confirmed by the Court of Appeal in 2017, the judgement has now been upheld again by the Supreme Court, after a decision on June 6.

The question of who owns treasure should it be found on a property can be difficult to answer.

According to a report on the subject by news source LCI, legally, the value of any gold or other objects discovered on a site would usually be shared between the finder, and the owner of the property in question.

Any treasure that is found by the owner on a property, would also usually belong to them, except where the previous owners have not explicitly relinquished ownership.

For example, gold coins found behind a wall or in the garden would usually go to the current owner of the property - except in specific cases, as this new case has shown.

As Me Roumeau explains: "Here, the sellers of the house were able to prove that the gold belonged to them. It would have been different if my clients had discovered precious old Gaulois coins, for example, as it would be difficult to discover their first owners! That is what we would call loss of memory ownership."

The ownership of treasure found in more obvious places, such as a painting in an attic, would be less certain still, as an attic is often used as a place for keeping objects, so the previous owner of the house could rightfully claim continued ownership.

Any treasure with archeological value must be declared to the authorities, including your Mairie office, under the heritage code L.531, LCI explains.

Similarly, the definition of treasure is quite specific: if you have used a metal detector to find it, and did not come across it yourself organically, it is usually no longer known as "treasure".

However, in 2004, a Poitiers court decided that a cache of treasure discovered by metal detector was indeed worthy of the name.