Calls for a public inquiry into the mental health services of Norfolk and Suffolk have intensified, with campaigners and bereaved families adding their voices to the pleas.

But what would this entail - and why is there a demand for it to happen. Here is what you need to know.

Just what is a public inquiry?

A public inquiry is a major, in-depth investigation which deals with any matter of serious public concern.

They are designed as fact-finding exercises which set out to find what has happened, why something has happened, who could be accountable and what lessons can be learned to prevent recurrences.

How do they come about?

Public inquiries are generally convened by the appropriate government minister for the area they apply to.

Were a public inquiry to be held into the region's mental health services, it would need to be commissioned by health secretary Sajid Javid, who would appoint a chair, often a judge or a senior barrister.

How do they work?

Public inquiries are lengthy, forensic processes which involve gathering evidence form a huge range of sources.

Should one be called into the mental health services it would see the Norfolk and Suffolk Foundation Trust (NSFT) required to provide evidence, along with health leaders from outside of the Trust, commissioners and other local authority figures.

It would also see a call for evidence made which would invite anybody affected to get involved, whether that is families, carers, staff members or people who have sought services themselves. Members of the public are able to put themselves forward to participate in the investigations.

Once inquiries are completed, the chair will make various recommendations for how improvements can be made.

How would it differ from other investigations?

Much of the process would be similar to those carried out by the Care Quality Commission during its experiment.

The inquiry would explore practices within the Trust, hearing evidence from leaders, staff members and other interested parties in the same way.

However, a public inquiry would also examine the services on a much broader scale, rather than solely focussing on the Trust itself.

It could potentially be extended to examine the ways organisations like the CQC, NHS England and Norfolk and Suffolk County Councils have monitored NSFT's services and held it accountable to make improvements.

Who is calling for this and why?

The calls for a public inquiry are being led by Labour councillor and former mental health nurse Emma Corlett, who attempted to garner the support of Norfolk County Council for it this week.

She has been backed in her calls from the Campaign to Save Mental Health Services in Norfolk and Suffolk, which says that anything short of this "would let people off the hook".

The calls have also been backed by bereaved families of those who died while receiving care from NSFT.

Ms Corlett said: "Until a genuinely independent public inquiry into the disaster of the last 10 years is undertaken lessons cannot be learned and we cannot safely make decisions about what needs to happen next with our mental health services."

What does the Trust say?

Following its latest inadequate CQC report, the Trust has acknowledged that people have not been receiving the care they deserve and say it is dedicated to sorting this out.

A spokesman for the Trust said that should an inquiry be held, it would fully co-operate with it.

Have similar inquiries happened before?

Yes. While public inquiries into failings at individual health trusts are unusual, they have happened in the past.

One such occasion was the Francis Inquiry, which was published in 2013 and explored failings at the Mid Staffordshire NHS Foundation Trust.

Following this inquiry, some 290 recommendations were made, including one which led to a new regulation known as 'statutory duty of candour' requiring health providers to inform people of when things have gone wrong.

Another example of a public inquiry into a health matter is the Infected Blood Inquiry, which was launched after hundreds of people were given blood contaminated with infections such as HIV and hepatitis during transfusions.

Perhaps the most high profile public inquiry into a health issue is one that is yet to be held - with the government's response to the Covid-19 crisis set to be subject to one.

Other high profile public inquiries not related to health include ones held into the Hillsborough disaster, the Saville Inquiry into the Bloody Sunday massacres and the Manchester Arena bombings.

What are the advantages?

The main advantage is that public inquiries provide a far more forensic form of investigation than any other form.

They are able to cover grounds that may otherwise not have been covered and would be able to take a more systemwide approach to simply looking into the Trust itself.

It also ensures that pieces of evidence that might otherwise have gone untold are brought into a public forum.

What are the disadvantages?

The main drawbacks are cost and time. Public inquiries are extremely lengthy processes and are consequently extremely expensive.

The Francis Inquiry into Mid Staffs came at a cost of £13m. It saw 181 witnesses provide evidence over the course of 139 days.

The Saville Inquiry lasted 12 years and cost a staggering £195m.