If a driver is forced by direct threats of physical violence to transport stowaways, what is their legal defense under UK law, and what must they do?

1. They have no defense and must go to prison
2. The defense of duress; they must report the situation to the police at the very first safe opportunity
3. They can claim they are exempt from all laws because they were driving a commercial vehicle
4. They must keep the stowaways hidden forever to avoid prosecution