On an easy section of 'safe' sport crag in the UK, Abbey Buttress just off the M4 near Port Talbot my partner and I stopped off on the way back to Bristol from having been working at his house in west Wales for the day.

We'd climbed over a sandstone section already three times, as we were on the second route over the same bit of rock having climbed the other routes already, and my partner was going up to clean the route before going home, when a slab of it came away in his hands. I saw three lumps of rock and him flying down towards me, we think the middle sized bit that hit the back of my head judging from where I was in relation to the rock this makes sense. It measured around 0.4 x 0.3 x 0.1m.

I think I fell forward and also then hit the front of my head and somehow still arrested his fall. I don't remember this bit but it would seem I didn't fully loose conciousness and came back to being 'awake/alert' a few minutes later still holding the rope, by which point he's managed to calm himself, make himself safe, untie and start downclimbing. Thankfully he'd fallen far enough that it was only a few very easy meters he had to climb down. I called to ask if he wanted lowering seeing him above me but not having full vision couldn't tell he's already untied.

I was wearing a helmet and it no doubt saved my life and likely his, or at least his legs/back from a groundfall.

We went to A and E and the CT showed my brain and skull are okay, and I had a referral for a different hospital for stitches to the front of my face for the next day,.
I'm still pretty groggy physically and have a lumpy back of the head, I also currently look like a cross between a hamster storing lunch in it's cheeks, a character from star-wars. He's shaken mentally, which is maybe harder to heal, but we're so very happy to be alive and well, as it could have been fatal.