At their Spring conference six months ago Liberal Democrats voted to make ending child detention an Election promise. (‘The Government must find its long lost moral compass and put an end to child detention immediately,’ said Chris Huhne, then shadow Home Secretary.) Clegg pushed successfully for its inclusion in the Coalition Agreement.

Then the Home Office went to work. Instead of stopping the dawn raids and closing the asylum prisons, immigration minister Damian Green invited selected NGOs to join a ‘working party’ helping the government to review alternatives to detention.

Green announced: ‘All those who have the most knowledge of the asylum process should play a significant role in guiding us onto the right path.’ Behind their backs, he sanctioned ill-thought out draconian ‘pilots’ of ‘alternatives’, bundling vulnerable families out of the country without recourse to legal advice.

In a parallel and chilling show of true intent, the Ministry of Justice, ignoring appeals from scores of leading lawyers and the Archbishop of Canterbury, let the biggest provider of legal representation to asylum seekers — Refugee & Migrant Justice — fail, for want of prompt payment of fees owed by the government. RMJ’s collapse robbed many thousands of vulnerable people of legal advice, and thrust the surviving not-for-profit legal aid providers and specialist solicitor firms under catastrophic strain.

As for Damian Green’s review process, its integrity is manifested in the person put in charge of it. Dave Wood, a former police officer with no experience in children’s services, is director of criminality and detention at the UK Border Agency, locking up more than 1000 children every year in conditions known to harm their health.

Such is Wood’s enthusiasm for detention that he told the Home Affairs Select Committee last year that families rarely abscond but should be locked up anyway to deter others from coming here.

He wrote to the committee falsely undermining peer-reviewed medical evidence that Yarl’s Wood was damaging children’s physical health and messing up their minds. ‘The study was undertaken without any reference to the UK Border Agency or its clinicians,’ he told MPs. Not true. Home Office documents attest to the discussions that took place.

No maverick, Wood is a perfect product of his department’s culture. As recently as June, an eye-popping safeguarding report criticised the Border Agency for ‘fundamental’ child protection failings. Dismissing a mother’s desperate pleas for medical care for her five year old, sexually abused at Yarl’s Wood, the Border Agency (catchphrase: ‘treating children with care and compassion is a priority’) swept mother and child out of the country.

The Minister for Children and Families, Sarah Teather — a Liberal Democrat — sent a friendly message to last week’s parliamentary launch of the Medical Justice report, reasserting the Coalition’s commitment to ending child detention, but adding: ‘We have to be careful not to rush into this as we are dealing with the safety and well-being of often vulnerable children and it is essential it is done properly.’

Quite how children’s safety might be served by not rushing to end a practice proven to wreck their lives is a mystery that suggests leading Liberal Democrats have been gulled by the detention enthusiasts at the Home Office.

Liberal Democrats may take pride in their end child detention pledge. But they must summon the political integrity to fight for it, or else the Home Office will swap one form of state sponsored cruelty for another. As Medical Justice concludes: ‘Ending the immigration detention of children should be immediate, and not contingent on any reviews or pilot projects on alternatives to detention.’