Arrived Glenridding 3pm easter sunday, weather was good that day but poor forecast for next day, Id been waiting years to ski down Helvelyn N face so decided to go late as conditions were good. Went up Swirral edge good views of proposed ski descent, crampons on up edge, practised grabbing axe from sack loop to ensure Id be able to reach it if needed. Got to top Helvelyn 6.20 ish, huge frozed cornice around top, accessed face on skis from top of swirral edge, traversed out into centre snow bowl area. Snow more hard packed/frozen than expected, first turn fell landed on back and started rapid slide. Tried to reach axe but sack had been pushed further down my back couldnt reach it, skis still on coul dnt roll over(not sure why). Right boot smacked hard into rock skis came off, still sliding on back getting faster, looked and saw lower boulder field approaching(thats when fear really kicked in!) Started using a pole as brakes and trying to dig boots in limited effect. Then by amazing luck I hit a protruding rounded rock , the impact was taken by sack strap and muscle on my left shoulder, stopped.(2 guys yelled from swirral to see if OK, I was sort of). Checked self over, blood from grazes on face, painfull shoulder, right ankle very painfull but realised it wasnt broken(had broken ankle few years previous). Then saw skis 250 metres up face, put crampons on got axe and clibed back up to retrieve skis, only just managed to load sack with skis onto back as shoulder hurt. Then position I was in hit home, it was getting towards dark, I still had to descend face while limping in crampons, got back to Glenridding 20.45 in dark.