Extensive plans for the restoration of the imperilled Fort Ricasoli were given the go-ahead by the Planning Authority on Monday, six years after they were submitted.

The plans by the government Restoration Directorate will see the restoration, in several phases, of large parts of the Kalkara fortifications – including bastion and parapet gun emplacements, ditches, ravelins, barrack blocks and a chapel – to ensure their long-term preservation.

Fort Ricasoli, built by the Knights of St John and the largest on the island, has been in a dire state of deterioration for years, with sections of its outer bastions already having crashed into the sea and heritage experts warning that further collapse was inevitable without immediate intervention.

A report drawn up by the Restoration Directorate as part of the planning process noted that the deterioration had largely been caused by the rough seas which continuously batter the exposed ramparts.

The report concluded that wave action had caused extensive structural damage to the bastions facing the open sea, causing their collapse, while salt contamination had further attacked masonry elements and rock outcrops.

Extensive rust damage was found on steel structural elements and fittings added in later years, while further damage had been caused by the unchecked growth of algae and vegetation, neglect and lack of maintenance, as well as pollution from the burning of fossil fuels.

Sections of bastions already crashed into sea

The planned restoration works include cleaning and reconstruction missing sections of the limestone fabric, restoration of deteriorated masonry and collapsed structures, and structural consolidation.

The rock face below the fort will also be consolidated as a hazard reduction measure.

Although the application for the works was submitted in May 2013, it appears to have lain dormant for years, and was only approved by the PA on Monday.

The Restoration Directorate did not respond to questions on why the plans were delayed and where they fitted in the broader strategy for conserving the fort.

Concerns over the fort’s survival have increased in recent years, and heritage group Wirt il-Kalkara last year estimated it would take €50 million worth of emergency works to ensure its survival.

Designed by the Italian military engineer Antonio Maurizio Valperga, the fort was built between 1670 and 1698 on a promontory known as Gallows Point, commanding the entrance to the Grand Harbour. Over the centuries, it was occupied and added to by the Knights of St John, the French and, finally, the British army and Royal Navy, before being decommissioned in the 1960s, since when it has been used for industry and as a film location, including for Gladiator and Game of Thrones.

It is a Grade 1 scheduled national monument and has been on the tentative list of Unesco World Heritage Sites since 1998.