14 May 2021, 17:21 BST Cyclists make their way through Pembrokeshire Coast National Park in West Wales. Sustainable travel is complicated and, as Fran Cellet explains, even the term is flawed. Photograph by 4Corners Images Do you remember all the fuss about plastic straws? It wasn’t long ago when company after company realised that handing out 4.7 billion plastic straws each year in England alone wasn’t such a great idea after all. Hotels were quick to jump on that ‘green’ bandwagon. It was a clear win: something easy to phase out, that represented both a cost saving and a simple way of showing a brand’s eco credentials.