By "breaking contract", guessing wildly, I would imagine we are referring to leaving before one's training bond is amortized.
Without knowing the background I can't be specific of course, but a lot of people seem to be under the impression that merely leaving within the bond amortization period constitutes "contract breaking" - correct me if I'm wrong, chaps, but as long as the individual concerned actually pays back the appropriate amount of wonga, I would have thought he would be complying admirably with his contract.