This code system https://fhir.nhs.uk/CodeSystem/Ambulance-HandoverDelayDetail defines the following codes:

CodeDisplay
01Patient handed over within agreed handover period
02No capacity in the department
03No cubicle / isolation capacity
04Clinical condition of the patient requires continued support from ambulance staff
05Crew diverted to other department
06Patient taken straight into resuscitation
07Other major incident
08Complex clinical handover and/or care need (e.g. concurrent safeguarding need/bariatric bed required)
09Unknown