Something that has worked for me in other similar situations.
Drill two small holes in the end of the bolt, side by side.
Get a big old screwdriver, or a piece of flat metal bar. File or grind a ' V ' shape into one end. This then allows you to put the prongs of the fork you have just made into the holes in the bolt and turn it.
Alternatively, you can just drill one hole in the bolt, off centre, and use an old screwdriver and hammer to tap the bolt round in the direction you want. This can work well if the bolt has siezed, as the hammer blows will help to free it.