This is an important question. All managers in the UK are required to follow the law, including laws that touch on health and safety. There is no one who is exempt, no matter how high up in the business world they are. More specifically, there are three laws - English common law, Northern Ireland law, and Scots Law, depending on where the company is. All managers are obligated to uphold these laws and the accountability comes in through many levels.
First, the person should be accountable to himself or herself. In other words, all managers should know the law. Second, all companies have a structure of plurality for accountability purposes in place. So, one manager should be accountable to another. And of course, the direct superior is also accountable for those under him or her. Finally, there is the board of the company that is accountable as well. Hence, the very structure of companies are built for accountability. I should also mention that there are also outside auditors that seek to keep the company honest as well.
With this stated, often times, corporations and managers seek loopholes and creatively circumvent these laws. However, laws are meant to be followed, even the spirit of the law. If you consider the corporate problems in our world today, some of them are due to lies and others are due to following the letter of the law, but breaking the spirit of the law. The BP oil spill is a case in point.