Few leaders can match Sultan Qaboos’ charisma, stature and overarching appeal. He was a colossus of a statesman who was a formidable symbol of stability in the Middle East. He spearheaded Oman’s renaissance and prosperity, introduced what amounted to a written constitution, created a parliament and played the quintessential international mediator between adversaries, a role that elevated his nation’s stature as ‘the Switzerland of the Middle East.’

Many Western and Arab diplomats view Oman as a sparkling model of balance, thanks to his remarkable political sagacity. During the British-trained Sultan’s reign, Western nations repeatedly turned to Muscat to act as a mediator in tackling prickly regional issues.

When Americans or dual nationals with Western ties are detained in Iran or areas under Tehran’s influence, communiques that later announce their freedom routinely credit the help of Oman.

He signed a deal to let US forces use Omani facilities for emergencies.

In 1981, Qaboos began widening political participation and free elections for an advisory council were held in 2003.

The Sultan’s greatest diplomatic feat came as Oman hosted secret talks between Iranian and US diplomats that led to the 2015 nuclear deal between Tehran and world powers. The agreement, which limited Iran’s atomic programme in exchange for the lifting of economic sanctions, has been undone since President Donald Trump withdrew from it in May 2018.

He invested billions of dollars of oil revenues in infrastructure and building one of the best-trained armed forces in the region.

Under Qaboos, Oman trammelled uncharted territory in foreign policy.

Oman also acted as a mediator between Iran and Iraq during their eight-year war. It has also long served as a quiet base for US military operations.

Qaboos foresaw a modern, prosperous, and peaceful Oman, and he realised this vision. The 79-year-old leader transformed his nation from one with only three schools, no electricity and radios to a lodestar of economic development in the region.

In 1981, Qaboos began widening political participation and free elections for an advisory council were held in 2003.

Not many know that he had three major passions: reading, music and yachting. His colourful turbans stood out, as did his form-fitting robes with a traditional curved khanjar knife stuck inside, the symbol of Oman. He occasionally wore a white turban.

The Sultan’s death comes at a very sensitive time, following the killing of a top Iranian commander in Iraq.

Any threat to Oman’s stability could have unwelcome implications for the global oil trade – 40 per cent of sea-borne crude exports are shipped through the Strait of Hormuz separating the Sultanate from Iran – and for relations between Tehran and the West.

How Oman will respond to pressures both external and internal in a nation Sultan Qaboos absolutely ruled for decades remains in question.

It will be very difficult to imagine an Oman without Qaboos. At a time of regional volatility, particularly in the standoff between the US and Iran, his diplomacy is now needed more than ever.

There are apprehensions over what the scenario will be now that the ultimate stabilising force is no more.

For the new ruler, Haitham Bin Tariq, filling Qaboos’ shoes could be a very difficult step.

In a televised speech, Haitham promised to uphold Muscat’s policy of peaceful coexistence with all nations while further developing Oman. “We will continue to assist in resolving disputes peacefully,” he said.

Born in 1954, Haitham, who studied at Oxford, had served as minister of culture and as foreign ministry undersecretary. He was appointed in 2013 to chair Oman’s development committee.