STEPHEN Hillier only ever had one ambition when he was growing up.

His dream was inspired by his father, Victor, who had served as a leading aircraftman in the Royal Air Force during the war and been a wireless operator in a mobile signals unit in India and Burma. “When I grew up I wanted to do nothing else apart from join the RAF and fly aircraft,” his son recalled.

His destiny, indeed, had been shaped when he was just four years old, when his father bought him a Ladybird book, The pilot in the RAF. That was the “pivotal moment,” he says. “That is undoubtedly my inspiration.”

Now Hillier, once a pupil at Kilmarnock Academy, and formerly station commander at RAF Lossiemouth, is Air Chief Marshal Sir Stephen Hillier, KCB CBE DFC ADC MA RAF, Chief of the Air Staff. He is, in the words of the RAF, the 4-star commander and professional head of the Royal Air Force, accountable to the Defence Secretary for the force’s fighting effectiveness, efficiency and morale.

Hillier was in the news last week when he warned that Britain’s armed forces must be ready to fight countries such as Russia in space. If Moscow was prepared to initiate a chemical weapons attack in this country (on the former Russian spy Sergei Skripal and his daughter Yulia), it could also defy international rules on such issues as deploying laser beams or jamming devices to put key satellites out of action.

He said the RAF, which is celebrating its centenary this year, was at the forefront of efforts to respond to the increased hostility from Putin’s Russia. No one, he said, had expected a return to the “potential state-based conflict and threats from Russia … Military-grade nerve agent being used for attempted murder on the streets of our country; the reckless and indiscriminate bombing of civilians in Syria. The illegal annexation of Crimea, the first time since the Second World War that one sovereign nation has forcibly annexed territory from another in Europe; the criminal activities of the Russian state in cyberspace.”

Hillier said the air and space environment had changed. “For the past 30 years, control of the air has been almost a given … We haven’t had to worry about anybody trying to constrain what we do in the air environment. That is now fundamentally different, as we have seen graphically demonstrated in Syria.

"Control of the air is the RAF’s primary mission, as it is in any air force. We are back to the business of needing to fight for that control of the air. That requires sophisticated capabilities and it requires a balance of effort, which is different for air power than we have seen in the past.”

He made the same point in January when he held up a photograph of two RAF Typhoons escorting a pair of Russian TU-160 bombers that had strayed close to UK airspace. “That’s 30 miles off Aberdeen,” he said. “I am not saying they were about to attack the Embankment in London. [But] we need an independent air service that is able to protect air space above the UK. That continues to be our number one priority.”

Sir Stephen – he and his wife Elaine have two grown-up children, Rebecca and Alexander –joined the RAF in 1980. Within eight years he was a Tornado GR4 pilot and a flying instructor. He has recorded more than 3,500 flying hours and “extensive operational and command experience”, ranging from squadron pilot to theatre commander of British forces.

He flew 16 combat missions over Iraq as part of Operation Desert Storm in 1991. In 1999 he was awarded the Distinguished Flying Cross (DFC) for operations over Iraq. He was one of 11 officers to be conferred with gallantry awards by the Queen at Buckingham Palace in February 2000. The BBC said it was the largest number of such awards received in one day since the Second World War.

In October 2003, 15 RAF service personnel at Lossiemouth were honoured for their actions during the hostilities in Iraq. Hillier was presented with the US Bronze Star. "From my perspective,” he said, “I'm absolutely delighted at the level of recognition for the station. RAF Lossiemouth's contribution to the operations in Iraq was absolutely pivotal."

He won a CBE in 2004 and continued to make steady progress through the ranks of the RAF. He was knighted in 2014. He was Air Marshal in October 2015 when he was put in charge of the Navy’s £6.2bn aircraft carrier project. The Daily Mail greeted the appointment with the headline, "Landlubber is handed top Navy job". He has also been described as a “safe pair of hands” who was a key architect of the 2015 defence review. He was appointed Air Chief Marshal in July 2016.

His reasons for choosing, in 2016, as his must-read military book of the year, one about the Burma campaign of 1944 make interesting reading. It was, he said, a “timely reminder from history of the importance of controlling the air, and the RAF's vital role in a hard and often forgotten campaign.” But it was also, he wrote, “a personal reminder of the part that my father played in that jungle campaign.”