As we're leading, yup you guessed it, one screw came off and his bit was hanging there. Fortunately my trainer/ friend was also on the ride so he took the bridle off the horse he was riding and gave it to me to use and he used his halter and lead rope. So, everything went fine and I didn't have to lead Walka the rest of the ride as I thought I may have to.
Moral to this story, don't put off what you know you need to do before something happens. Also, I am now packing an extra bridle and bit and my leather strips.