I can't reveal my plans, now, how could I? 😉
No matter how hard you tug and struggle, you have to give in.
The chains were hammered in place: they are plain unpickable and unbreakable.
You can only guess many other slaves tried fleeing, before, and the slave-drivers had to plan accordingly.
The wagon must be built around thick iron rods, and metal loops were welded shut in the making.
Nothing sort of a fully equiped squad of Kathic smiths can pry you free from this predicament: the slave train is pretty much escape-proof.