as said the bolt is recessed but you can get on it with a ratchet just to hold it while you undo from underneith.
The knucke bolt is usually a bit seized. Any form of penetrating oil and spray on. I used wd40 as thats all i had, in extreme cases have herd mention of plus gas.
Then get a wedge shaped something, coal chisel ?, and hammer it into the slot to spread the clamp. wedge it open and leava wedge in there. Then hammer the top of the knuckle by what ever means. I used a long punch at an angle down through the strut gubbins. Be carefull the wedge/cole chisel does not go in too far and hit the knuckle. And and be aware that wishbone will very nearly as far down as travel will allow, so you will have to push it down to clear the knuckle from the strut when it does free. I have on occassion been hammering away to find its been bouncing back up into the hole.
If you cant hammer on the knuckle directly with a punch. Try a long bar of some sort, maybe another hammer or prie bar and place it horizontal with one end on the pin and hold the other while you hammer on that as near to the pin end as you can. Hth