To continue the hypothetical, because I am curious as to how my character could get out of this perceived 'untenable' situation is there anything stopping him from.

1. Crouching and dragging his sword down, before thrusting it into Florian's stomach.
2. Kicking Florian in the leg or balls if he's feeling particularly cruel with his left leg.
3. Pommel striking Florian in the face
4. Stepping back with his right foot 
5. Dropping his sword and breaking Florian's hand/arm
6. Punching Florian in the face or stomach.

If Florian moves his sword to deal with any of these threats, he may have stopped Brennus, but Brennus' sword would have an open target to his head and neck, except for option 1.  

This is a chance for you to show me something about sword fighting while I explain how in a purely Arena sense your posts are lacking some detail etc. 

It's worth pointing out that your personal experience seems to have been somewhat restricted in what action you can take (I'm guessing fencing?) so though the situation may seem untenable in that strict regimented sense, there are probably a lot of ways you could essentially cheat to escape or gain an advantage. An example I always think back to is how kicking someone in the balls in MMA is disallowed, and immediately halts the fight, despite it being incredibly effective, or even doing the same in boxing. People who have real life experience have a lot of knowledge about what is essentially 'sport' and though its definitely applicable to a fight which is trying to represent real life, there are some 'cheat moves' that I will happily use, which are outside of that sporting environment.