This is one pic I have always admired too.
I too believe it is a fake - unfortunately - it is hot!
I feel it is a combination of two pics - on for the 'headless' body with the other where the head is. Well done though.
The head is not in a natural position for just being removed.
The 'executioner' has a sword - if beheading with a sword the victim is kneeling upright or slightly bent - not over a barrel or block.
Whether I am right or wrong it is still a damned hot pic!