More good ideas.
I actually have a very good £400 metal detector which I've not used much, a Tesoro Cebola (Laser Trident 1), that was on my 'one day I must...' list. It can pick up a 1p at about 16" depth and has a discrimination function to hone in on different metals. I predict a fine haul of brass shotgun cartridges and car parts from the travellers, but I can use a trowel with one hand to dig. In the old pond at a depth of 2m we probably have 20 tons+ of scrap metal, courtesy of when the council used that bit as a tip. It now is my parking / proposed shed area.
I also have some orange vet wrap, which ironically you can see on the handle of the tool that did the damage ! I got it to provide grip on the otherwise slippy handle, but it would serve tp protect the cast from muck.
Its going to be long haul, a consultant this morning explained I'll be given a removable cast and as of next week will need to occasionally use it very lightly for physio and prescribed exercises, but no more, or it'll snap and not be repairable. Tendon injuries are apparently far worse than a break, especially on someone active who is impatient to use it. NHS have so far been brilliant, can't fault the care I've had.