Last week, a team of scientists at the JET laboratory in England announced a major step towards making what some hope will be the energy source of the future.   Nuclear fusion offers the hope of producing near-limitless supplies of safe, clean energy to power our homes, workplaces and cities.   It is also one of the greatest engineering and scientific conundrums that humankind has ever grappled with.   It took decades of research to get to a test that only lasted five seconds. There is still a long road ahead.   But those leading the quest are hugely excited by what they saw.   On this week's Beyond the Headlines, host James Haines Young asks: will nuclear fusion save mankind?