Tom Thankyou.
As I see it this answers the second sentence of the guidance:
Nor does the defence apply to an employer where failure to comply with the provisions of the Order is due to an act or default of his employees or appointed competent persons.
The appointment of a fire consultant to carry out a fire risk assessment will be a contract for service. The employer will remain liable, quoting from the Lawteacher website
"An employer will usually be liable for (a) wrongful acts which are actually authorised by him, and for (b) acts which are wrongful ways of doing something authorised by the employer, even if the acts themselves were expressly forbidden by the employer (Salmond & Heuston on the Law of Torts, 1996, p443)."
Hoowever why should it be necessary to specifically re-iterate in the Order an accepted principle that has been universally applied elsewhere?
This still leave the first element unanswered:
"The defence of due diligence does not, however, apply where the responsible person is alleged to have failed to have taken such general fire precautions as will ensure the safety of his employees, or to have failed to eliminate or reduce the risk from a dangerous substance present on the premises."
Or am I still missing something? Why is is it necessary to create the defence of due diligence and then remove it if the persons at risk are employees? Perhaps I am misinterpreting the intent of the Order.