On a point of accuracy Kurnal, while you were grovelling in a basement, I was doing inspecting officer training at the REAL Fire Services College in God's own country, amongst God's chosen people, whom he has blessed with a beautiful country and the most decent genuine people in the World, though so as not to show too much favouritism to his chosen ones, he landed them with lousy neighbours and the Rt Horrible Tony Blair and the odd character of Gordon Brown.
On your question, I keep telling you it is incredibly simple and I do not know how to make it simpler. A fundamental tenet of the EU Directives is that an empoyer is UNCONDITIONALLY responsible for the safety of his empoyees, so due diligence as a defence would not wash. The EU do not even think the UK should have so far as is reasonably practicable but the UK were bullish about that , even though the EU thought it was a qualification that conflicts with the strict liability of an employer.
This responsibility cannot be delegated away, transferred to a fire risk assessor regardless of whether he is registered, circumcised, baptised, glorified or cannonized. nor can it be sold on ebay, given away as a present, or put up for auction. It stays with the employer. Whether an EA chooses to prosecute the employer of course is up to them. They may decide to prosecute an Article 5(3) person instead or to prosecute the RP AND an Article 5(3) person. It probably depends which one got up the nose if the I/o in England, or, in Scotland, whom a properly qualified and very bright lawyer at the PF thinks it is appropriate to prosecute, taking public policy into account and not wishing , as has happened in the case of a large met F&RS in England, the cost of defending frivolous charges that are then dropped, being paid for by public funds (ie you and me).