In his maiden electoral speeh in 'Free For All' Number Six states that he intends to disocver who are the Prisoners and who the Warders. In 'Checkamte' Number Six is given a lesson from Number Fourteen on precisley that matter. It's the same as in life, you judge by attitudes, you soon know who's for or against you. But having done so, it is Number Six's authority which causes the Rook-Number Fifty-three to put to Number Six his own test, and is found to be a Guardian!
In the end it does Number Six no good to discover who are the Prisoners and who the Warders, his air of authority he took when he set out on this little adventure, caused a bit of a mix up, with Number Six accusing the Rook-Number Fifty-three of being one of 'them.' Originally the script for 'Checkmate' did call for a 'plant' to merge with Number Six's reliable men. But Number Six saw through him, and told him to go away. It's a pity that the idea of a 'plant 'amongst the men Number Six found to be reliable, because what better way to find out what Number Six is up to.
Be seeing you