Winter ascent of Helvellyn, initially poor visability above approx 600metres which along with snow obscurring the paths made for trickier route finding. Visibility improved dramatically about 15 minutes after summitting which lead to a decision to extend the walk along North along the ridge to Stybarrow Dodd. Elective return in darkness to make most of winter day. I shared responsibility for poor visibility and night navigation. This was my first significant ascent in the Lake District and my first mountain day in full winter conditions.