The inquiry is focused on care provided by Essex NHS mental health trusts over a 24-year period.

Baroness Lampard said: ‘We will seek out the truth. In doing so, we will not simply accept the information we are given but, instead, we will question and challenge the evidence until we're satisfied that the findings we make are the truth or as close to the truth as we can come.'

The sessions, which will end on 15 May, will include a further six public hearings over next 18 months.

Baroness Lampard added: ‘We are investigating the big, critical concerns about what went wrong that span across over almost a quarter of a century. The inquiry will dive down into these systemic issues with increasing focus and detail, until we have enough evidence, information and understanding to satisfy ourselves about what really happened and why, so that I can report my findings and make meaningful  recommendations for change.'

The chair said the hearings would include the legislative and policy background and guidelines for good medical practice in the delivery of mental health services nationally over the 24-year period the inquiry was concerned with.