Unlucky mate!
I nearly joined you on the ground (in a sense). I was riding round saltersgate on the a169 this afternoon, basically its a tight down hill right hander...
Going down there at about 10 MPH (Slow yes) with back brake on when i lost all grip and the bike went a little sideways
luckily i mantaged to instinctivly react and kept it up and going but it was a bit of brown pant time i can tell ya!
When i got back.