The BBC's Newsnight reports on the test case

The case could mean tens of thousands of people with learning difficulties and mental health problems having to be reassessed.

The Lords began hearing the case of an autistic man, known as Leonard, on Tuesday. The hearing is expected to last until Thursday.

It follows an earlier Appeal Court decision that Bournewood hospital in Surrey was acting illegally by detaining him without his consent. He is now living with his carers.

Sectioning

If the hospital loses in the Lords, it will mean a huge increase in the use of sectioning under the Mental Health Act.

Campaigners discuss the impact of the case

Hospitals and nursing homes argue that this will increase bureaucracy and attach more stigma to people with mental health problems and learning difficulties, including elderly people with dementia.

The Department of Health is supporting the hospital.

Rights

But opponents say it is a question of patients' rights. They believe mental health patients should be entitled to a regular review of their cases, which would be guaranteed under the Mental Health Act. The present informal admissions policy allows for abuse, they say.

'Leonard' was hospitalised without his consent

It is still unclear what the practical implications will be for nursing homes and hospitals.

The Department of Health says it will issue guidance after the outcome of the Lords hearing is known. This should be in around two months' time.

The NHS Confederation says it will force homes to change the grades of staff they employ for patients with dementia.