After the ICO said that the evidence it had received regarding this was insufficient, Hamilton turned to solicitors. Its legal team then mounted a defence on the grounds that Hamilton had not been the instigator of the messages (despite stating previously that they had ordered them), and also that the Commissioner couldn't prove that it hadn't obtained consent
Why would you not be the instigator? You either asked for them to act on your behalf or you didn't.
This other company in Belize, why would they send messages advertising your services if they weren't being paid by you?
You might not have sent the messages but it was your responsibility to make sure the messages were sent in accordance with current regulations.