I would go to the training/induction and bide your time. Then if and when the ideal job comes through, write a letter to whoever, explaining that you feel this is not going to be the right position for you, and that in thinking about the company's best interests, it is better for them that you leave now, so they can find someone more suitable for the position, as you realise this isn't you. But for goodness sake, wait until the other job is definitely in the bag first. Say nothing till then.