How hard is walking 12 miles for Duke of Edinburgh silver award?

The only way to really prevent blisters is to practice for your 12 mile journey. Start walking now 2-4 miles everyday and work your way up to 12 miles. Yes walking 12 miles for the first time without practice will be a little difficult. Bring an extra pair of socks to change about half way through the walk. That will help with the blisters.