This is where a deadman or a stake can come in handy.

I was already belaying off the deadman... He eventually got a stake into some ice, but it was incredibly sketchy. Scariest climb yet for both of us.

Situations like this are fundamentally unprotectable. Only options are extreme bravery or evasion. Just out of interest, where did he attack the cornice?

The cornice petered out a little to the left of directly above, second notch in the skyline from the left in the photo. Chris said it looked like somebody had bashed through there a few days before so it wasn't as bad as it could've been.