The sound of Kenyan women singing, the smell of the first rain after the dry season and the taste of fresh mango – these are some of Niall Ferguson's boyhood memories. Nairobi, his home for two years in infancy, was newly independent but still felt like the world of White Mischief. Empire had been kind to the Ferguson family; an uncle's first job was in Kolkata, a great-aunt had a home on the Saskatchewan prairie, his grandfather travelled to South America to sell liquor to Indians.

So it was something of a shock to arrive at Oxford in 1982, and find that fellow students failed to share his sunny view of Britain's colonial past.

Ferguson's career as a student politician was prematurely ended, he remarked years later, by a decision to speak up for empire at an Oxford Union debate.

Thirty years on, Ferguson has a new platform; he is the 2012 BBC Reith lecturer. The first of his lectures, the Human Hive, is broadcast on Tuesday morning on Radio 4. But his views remain defiantly at odds with the left, combining a defence of imperial history with a justification of present-day military adventures – from Iraq and Afghanistan, and now, Iran.

War can be a lesser evil than appeasement, Ferguson wrote in an article for Newsweek in February. He declared: "The people who don't yet know that are the ones still in denial about what a nuclear-armed Iran would end up costing us all."

A month after the invasion of Iraq, he described himself as "a fully paid-up member of the neo-imperialist gang"....