So far the volunteers have successfully been losing lost weight, but now the honeymoon period is over. It is the final two months of the diet, and their minds and bodies are fighting back. Dr Chris van Tulleken and Professor Tanya Byron find out if the new personalised diets will help them stay on course, and the experts reveal the scientific secrets to permanent dieting success.

The Milky Way, our galaxy, is a magnificent sight in the night sky, but we know surprisingly little about it for certain. What is its shape? How many stars does it actually contain? What lies at its centre? The Gaia space telescope will answer these questions, being armed with the most advanced camera to leave our planet, and it will allow us to see our galaxy as we've never seen it before. The Sky at Night visits the factory in Chelmsford that made the astonishing sensor at the heart of the mission.

Between the 1920s and the 1960s the world's great powers sent vast military-style expeditions to conquer the peaks of the Himalayas, with Everest at their head. This was a great game played - camera in hand - by Imperial Britain, Nazi Germany and superpower America. As a result, Himalayan mountaineering's most iconic, epic and tragic moments didn't just go down in history, but were caught on film - from the deaths of Mallory and Irvine on Everest in 1924, to Everest's final conquest in 1953 by Hillary and Tensing. Using footage never before seen on British television, this is the story how of how film-makers turned the great peaks into great propaganda.

Tim Whewell is in St Petersburg to meet the self-styled Russian nationalists and patriots who are volunteering to join the fighting in eastern Ukraine. He joins a group of volunteers as they undertake military training, and travels to Ukraine to see how the volunteer force is fighting on the ground.

Tom Service plunges into the life and times of Mozart to try and rediscover the greatness and humanity of the living man in his moment. Mozart's prodigious output and untimely death have helped place him on a pedestal that can often blind us to the unique brilliance of his work in the context of his life and times. Service visits the key cities and rooms in which Mozart lived and worked, plays some of Mozart's original instruments and scores, and gradually uncovers the brilliance and originality of his work." There is the prodigious childhood when Mozart was feted as an infant phenomenon around Europe's most glittering courts, and his golden decade in Vienna in which masterpiece followed masterpiece - operas, symphonies, piano concertos, string quartets - as if this short, high-voiced man-child must have been taking dictation from some divine source, until his death at the age of just 35 in 1791. Even more than the music, Mozart's tragic demise sets the seal on his myth. The trajectory of Mozart's life sets the template for the romantic paradigm whose throes we are still in today, which requires our creative heroes to die young to prove that they were too good for this madding world, whether it be Wolfgang Amadeus or Jimi Hendrix. Service travels from London to Vienna and Salzberg, unpicking the living, breathing genius that was Mozart. With Sir John Eliot Gardiner, Nicola Benedetti, Paul Morley and others.

From unexplained flashes in the night sky to flying saucers, this episode delves into the mysterious world of UFOs. How our drive to explain these bizarre phenomena, and desire to discover little green men, has in fact transformed our understanding of the universe