Did Local Authority A undertake the Section 2? If so, then Local Authority A is responsible for considering the Section 3. Section 13(1C) applies.
8.18 In certain cases, local authorities must also arrange for an AMHP to consider the case of a patient who is in a hospital outside their area. This applies where the patient concerned is already detained for assessment on the basis of an application made by an AMHP acting on behalf of the local authority in question. If that local authority has reason to think that an application for admission for treatment may now be needed for the patient, it is that local authority, rather than the one for the area in which the hospital is, or where the patient lives, which is under a duty to arrange for an AMHP to consider making the further application.
Yep, no debate. The local authority which arranged the s2 detention has statutory responsibility for arranging the s3 assessment.
The other local authority can agree to undertake the assessment (s13(5)), but they have no statutory duty to do so.
The AMHP lead should be fully aware of the responsibilities set out in s13. This issue has been discussed to death over recent years.
I suggest the hospital contact the relevant AMHP leads direct.