So you have your policy and your audit is completed so you know where the gaps are. How do you know if your system is working in practice?
That's where site inspections come in and they are essential to ensuring your systems are effective and that you are legally compliant.
Often clients do their own site inspections, sometimes at every level of their personnel structure and this is to be encouraged. People will have different perspectives and the more the better.
However, at reasonable intervals it is prudent to get the experts in just for that extra peace of mind.