I always carry a first aid kit in my back pack, just a small one from Boots. It has sterile wipes, gloves, various plasters, small dressings and a bandage. I added a couple of viles of sterile water for eye or wound flushing and a tube of anticeptic cream. I also always have a foil blanket with me, that would probably be the most useful thing. Fortunately I have never had to break out the supplies, but you never know when you might take a tumble or come across somebody else who is having a bad day.