A French court on Wednesday handed an 18-year prison term to an Italian man accused of orchestrating the kidnapping of an ageing hotel heiress in the French city of Nice four years ago.

Giuseppe Serena, 67, was among 13 people on trial over the plot against Jacqueline Veyrac, owner of the five-star Grand Hotel in Cannes and the ritzy Mediterranean seafront restaurant La Reserve in Nice.

Prosecutors accused Serena of seeking revenge for Veyrac's decision to terminate his contract to rent the restaurant in 2009 after it ran into financial difficulties.

Philip Dutton, a 52-year-old former British soldier who allegedly helped Serena and demanded the five-million-euro ($6 million) ransom for her release, was sentenced to 14 years in prison.

Six others were also given sentences of up to 15 years in prison, while five people were acquitted.

Veyrac, now 80, was snatched on the street on October 24, 2016, and bundled into the back of a van.

She was held bound and gagged for two days in the vehicle, which was parked on a quiet street, before being spotted by a passerby and released.

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