The Great Outdoors
                          
                          
                            Mountains of style
                          
                          
                            Today, down jackets built for K2 are worn on the school run and premium waterproofs pop up in pubs. In their photo book,  Max Leonard  and  Henry Iddon  track down hard-as-nails but unheralded mountaineers and the fabric innovators who put them safely – and sometimes even stylishly – on summits to ask how we got here