FII is an uncommon form of child abuse which challenges the very core of the doctor-patient relationship. The unspoken contract of “You tell me what's wrong and I'll do my best to help you.” is breached by a parent who fabricates their child's symptoms and sometimes even their physical signs. Anecdotally these diagnoses tend to be very delayed and children often suffer extreme harm in the process. In 2002 RCPCH produced the first definitive guidance on FII. In 2008 the Government produced updated guidance for all professionals which led to RCPCH producing a new Practical Guide in 2009. This paper incorporates much of the 2009 RCPCH guidance and is intended to be a brief guide for the busy Paediatrician who may come across one of these most difficult and time consuming cases.