Without us noticing, modern life has been taken over. Algorithms run everything from search engines on the internet to satnavs and credit card data security - they even help us travel the world, find love and save lives. Professor Marcus du Sautoy demystifies the hidden world of algorithms. By showing us some of the algorithms most essential to our lives, he reveals where these 2,000-year-old problem solvers came from, how they work, what they have achieved and how they are now so advanced they can even programme themselves.

Travel from the inner solar system to the Kuiper Belt and explore the moons surrounding the planets of the solar system. Many of these moons that were once unknown are now on the cutting edge of astronomical study. Some burst with volcanic fury another spews icy geysers and others offer the possibility of alien life. Are these strange worlds simply hostile environments unfit for humans or do other possibilities exist? Cutting-edge computer graphics are used to bring the universe down to earth and to imagine what kind of life forms might evolve in alien atmospheres.

We are in the grip of an allergy epidemic. 50 years ago one in 30 were affected, but in Britain today it is closer to one in three. Why this should be is one of modern medicine's greatest puzzles. In search of answers, Horizon travels round the globe, from the remotest inhabited island to the polluted centres of California and the UK. We meet sufferers and the scientists who have dedicated their lives trying to answer the mystery of why we are becoming allergic to our world.

A decade after An Inconvenient Truth brought climate change into the heart of popular culture comes the riveting and rousing follow-up that shows just how close we are to a real energy revolution. Vice President Al Gore continues his tireless fight, traveling around the world training an army of climate champions and influencing international climate policy. Cameras follow him behind the scenes-in moments private and public, funny and poignant-as he pursues the empowering notion that while the stakes have never been higher, the perils of climate change can be overcome with human ingenuity and passion.
Renowned filmmakers Bonni Cohen and Jon Shenk have taken the baton from 2006 Academy Award-winner Davis Guggenheim. What started then as a profound slide show lecture has become a gorgeously cinematic excursion. Our extraordinary former vice president invites us along on an inspirational journey across the globe that delivers the tools to heal our planet. The question is: Will we choose to take the baton?

Buddhists, Hindus, and hundreds of thousands of travellers from around the globe flock to Cambodia every year to experience the grandeur of Angkor. Its famous temples were built over the span of five centuries by the rulers of the Khmer Empire, and endure today as one of Earth's greatest archaeological wonders. Join us as we shed light on one of the most enigmatic, mesmerizing civilizations in the history of mankind. We peel away the myth and legend to uncover the hidden story behind the creation of this ancient city.
Angkor Wat is the largest temple on the face of the Earth and is a symbol of one of the greatest empires in the history of Southeast Asia. And yet, for centuries, the sacred structure remained lost within the tropical forests of Cambodia, along with the history of the young king who built the temple. Discover the story of Suryavarman II and how he ushered in the golden age of the Khmer Empire. See how Angkor Wat was constructed over four backbreaking decades, and witness the monument in its true glory and splendour, as it appeared 900 years ago.

During a Gurkha recruitment Palin is disturbed by Maoist insurgents, but survives to suffer as he climbs to 15,000 feet and sees the majesty of Annapurna Sanctuary. In Kathmandu he is blessed by the Nepalese king before meeting some holy men. Crossing into Tibet, he meets his first yaks at the highest monastery in the world, before heading up the Rongbuk glacier towards the summit of Everest.