The Reith Lectures episodes available now on BBC iPlayer

4/5. Assessing the role of security and intelligence services in a democracy.

3/5. Eliza Manningham-Buller reflects on 9/11 in the first of her Reith Lectures 2011.

2/5. Aung San Suu Kyi examines what drives people to dissent in the second Reith Lecture 2011.

1/5. Aung San Suu Kyi explores what freedom means in the first of the 2011 Reith Lectures.

4/4. Prof Rees calls for the UK to stay at the forefront of scientific research and discovery.

3/4. Professor Martin Rees explains where the limits of our scientific knowledge lie.

2/4. Does science have the answers to help us save our planet?

1/4. Prof Martin Rees asks who we should trust to explain the risks we face.

4/4. Professor Sandel makes the case for a moral and civic renewal in democratic politics.

3/4. Professor Sandel considers how we should use our ever-increasing scientific knowledge.

2/4. Michael Sandel asks what role, if any, there is for moral argument in politics.

1/4. Prof Michael Sandel considers the expansion and moral limits of markets.

4/4. Spence discusses how Chinese ideas of sport and athleticism have slowly evolved.

3/4. Spence explores the relationship between China and the US over two centuries.

2/4. Spence examines China's relations with the United Kingdom through three centuries.

1/4. Spence reflects on China's most enduring thinker, Confucius.

5/5. Jeffrey Sachs calls for a new Enlightenment to help make globalisation work for all.

4/5. Jeffrey Sachs delivers the fourth of five lectures. He considers the challenges of poverty

3/5. Jeffrey Sachs talks about the need for international cooperation to achieve peace.

2/5. Sachs discusses China's emergence as an economic superpower and the effect on climate.

1/5. Jeffrey Sachs delivers the first of five lectures, recorded at The Royal Society in London

5/5. Daniel Barenboim considers the difference between power and strength in music and in life.

4/5. Daniel Barenboim examines how music has the power to bring people together.

3/5. Daniel Barenboim argues that classical music can and should be accessible to all.

2/5. Daniel Barenboim examines what he calls 'the neglected sense'; the ear.

1/5. Musician and conductor Daniel Barenboim examines the physical phenomenon of sound.

5/5. In his final lecture, Lord Broers explores the responsibilities of the technologist.

4/5. Lord Broers explores the origins and impact of nanotechnology.

3/5. Does modern innovation demand new approaches to product development?