In the past two decades Rwanda has transformed itself from a society viewed internationally as a place of horror to one which is greatly admired. 

Even had modern Rwanda not emerged from such a dark past its recent achievements would be a beacon for the African continent. 

I will return to them shortly. But Rwanda’s past casts the darkest of shadows: your society instantly became emblematic of ‘the heart of darkness’.

And so the contrast between the darkness of the past and the brilliance of recent achievements is yet more remarkable than the achievements themselves. 

Rwanda has achieved and sustained rapid economic growth. Few other African countries have managed to do so. This is despite the evident fact that Rwanda’s opportunities are more limited: it is landlocked and lacks valuable natural resources. 

But more distinctively, the economic and social benefits of that growth have been widely spread across the society. We know this from independently analysed household survey evidence that has tracked progress. 

Elsewhere in Africa, even where growth has been achieved, the benefits have almost invariably been concentrated on narrow elites. To benchmark Rwanda’s achievement, in recent years the rate of poverty reduction has been as fast as in China, whose transformation has been an object of global astonishment.

Rwanda’s transformation has been achieved by a deftly managed but profound cultural change. At the heart of that transformation has been a new emphasis upon personal accountability. That process started with personal accountability for the darkness of the past. Those who had committed crimes against humanity were pursued and punished. But wisely, vindictive triumphalism was avoided. 

Leaders understood the grim lesson from global history that severe retribution launches vendettas that echo down the generations. Through a reasonable process of justice tempered by mercy, the past has been laid to rest. 

The same new culture of personal accountability has been vigorously introduced into the sphere of public service. Elsewhere in Africa, public sector workers commonly do not do their jobs properly. Teachers do not show up for class,nurses steal drugs, policemen and judges extract bribes. 

Similarly, many politicians abuse public office for personal gain. 

The consequences across Africa are appalling: the many services that government should be providing if a society is to prosper are woefully inadequate even though money is spent. 

In Rwanda such behaviour has been swept away. Public employees, officials, and politicians are all held accountable for clearly specified and time-bound goals. The consequences are already there for all to see: Rwanda is now a society that works. 

But I think that the full benefits of this transformation are yet to come. People perform better if they are held to account, but performance is also limited by skill. Rwandans are still in the early stages of learning the skills of modernity. 

Across the society, ordinary Rwandans now face a personal struggle to acquire the skills and aptitudes that enhance productivity: in simple terms, make them better at their jobs. Much learning happens simply on-the-job: it is called learning by doing. 

Elsewhere in Africa, learning by doing has often been detrimental: many public employees have learned the wrong things by doing the wrong things. In Rwanda workers are now doing the right things and gradually skills will diffuse through the society. 

But beyond learning by doing, people, both individually and in teams, can raise their performance through training. The rapid growth that is generating opportunity is also raising the return on new skills.

Improving personal performance depends, irreducibly, on personal effort. 

Ultimately, the philosophy of personal accountability that has underpinned Rwanda’s transformation is not primarily about taking responsibility for failure, it is about reaping the rewards of achievement. 

That, in essence, is the beacon that has been lit in Rwanda. Africa at last has a society in which justice has decisively replaced patronage. The results, both collectively and individually, are already remarkable. 

Sir Paul Collier is professor of Economics and Public Policy at the Blavatnik School of Government, Oxford University.