Well.. we think he got his leg stuck over the bottom wire of the fence, which is difficult as the bottom wire is about 80cm above the ground (due to a previous horse almost severing the fetlock on a lower wire). Vet was called and apparently he was very lucky not to do it a bit further up.
Tuesday 28th Feb: First day before the vet arrived
Saturday 3rd March: Looking a lot better but we had to call the vet again to sedate him to get the new bandage on! Note- the yellow stuff isn't pus/infection, it's yellow lotion xD (the green stuff is also something that the vet put on)
Monday 5th March: Looking much cleaner and healing quite nicely according to the vet. Bandage kept slipping so he's going nakey from now on xD (advice from the vet.)
Took another photo today as it's scabbing over and healing well. Now to play the waiting game! >.<