By not doing this course you may not be able to evidence your understanding of this subject.
You may also not know whether what you are saying, advising or recommending is legally correct, which can leave you open to a legal challenge possibly many years down the line.
How can you state that you are competent and more importantly evidence that fact if challenged to do so by a Freedom of Information request or possibly even in a Court of law?
How will you know if the decisions you are making and the advice, guidance and/or recommendations you are giving are actually reducing the risk when they may in fact be increasing it? That leave you very culpable and liable.
And it's not just you. If you are acting as an employed agent of an organisation you could be creating a liability for your organisation, which if it result in a serious injury and/or death could mean a major fine for your organisation, prosecution under various Acts of Parliament, a possible prison sentence for you and or another senior manager or director and the end of your career, because who would want to employ someone who had made that decision?
But most importantly, what about the personal cost to the people who will directly and indirectly affected by your lack of competence. The staff who run the risk of being assaulted at work and the service users who may be at increased risk of unnecessary injury or death.
Then there are the indirect costs that brings in terms of increased mental health and staff welfare issues leading to increased rates of absenteeism and staff turn-over, increased time and management costs in trying to resolve these issues, increased litigation and legal fees, legal challenges and industrial tribunals.
So I have one question for you. Why wouldn't you do this course?