In what's been billed as a 'world first', fast food grown in a laboratory was served up in London recently. HARDtalk speaks to Professor Mark Post who says his 'in vitro burger' could be the answer to our unsustainable appetite for meat and help ease the burden on the environment. There's clearly a need for more meat - the World Health Organisation estimates annual global production will have to double by 2050, so will meat grown from stem cells in a science lab ever make it to our dinner plates?