1. Familiarity of Grade - we expected some ice and awkward approach, but did not have the level of experience to define a Grade 1 vs Grade 3 vs Grade 4.
2. Familiarity of area. From the image, it's clear which area is the lower Grade, however we didn't have this view on the day or from the recommended approach.
3. More equipment than the Grade. We intended a Grade 1, so we did not bring any harnesses, rope, protection, etc. Just 1 ice axe and crampons each.
A second ice axe may have given more security for a descent. If we had knowledge of how and where to set up additional protection retreat could have been safer.
4. Recognise the retreat/point of no return. We climbed past a point that would not be safe for us to retreat from with the equipment we had, with the prospect of a safer point to settle and regroup being slightly higher.
5. Have some Emergency equipment on your immediate person - if the headtorch was in my rucksack rather than my pocket, it might not have been possible to locate us after night fell.
6. Register 999 - we were fortunate I had phone signal in the gulley.
7. Phone batteries will discharge quickly in the cold - have a backup battery and charging cable, and keep it in an inside pocket when not in use.
8. The wait for help will be long. Sing / Joke to keep spirits up and also to check responsiveness/health of the party. Hypothermia has some psychological symptoms (confusion and dropping of consciousness).