Video report by ITV News Political Correspondent Libby Wiener
A victim of domestic violence and the grandparents of a severely disabled teenager have won Court of Appeal challenges over the lawfulness of the so-called bedroom tax.
Here's what we know.
What happened today?
Two appellants argued that the government's spare room subsidy, was unlawfully discriminatory.
One case, brought by 'A' - a single mother living in a three-bedroom council house fitted with a secure panic room to protect her from a violent ex-partner - concerned the effect of the policy on women living in Sanctuary Scheme homes.
Paul and Susan Rutherford, from Pembrokeshire, and their 15-year-old grandson Warren brought the second appeal which concerned the impact of bedroom tax on families with disabled children needing overnight care.
Lord Chief Justice Lord Thomas, Lord Justice Tomlinson and Lord Justice Vos announced that they were allowing the appeals in both cases on the ground that the "admitted discrimination in each case... has not been justified by the Secretary of State".
The appeal comes after Mr and Mrs Rutherford lost a High Court challenge on the policy in 2014.
What is the 'bedroom tax'?
Government regulations, introduced in April 2013, have led to reductions in housing benefit payments to tenants in social housing who have been assessed through controversial "size criteria" to be under-occupying their accommodation.
The policy was dubbed the "bedroom tax" by Labour but the government rejects the term saying that the regulations remove what is in fact a "spare room subsidy".
It says that the policy encourages people to move to smaller properties and saves around £480 million a year from the housing benefit bill.
The policy has attracted criticism and sparked a u-turn by the Liberal Democrats, when they were in the coalition government with the Conservatives, who said it needed reform.
What was the legal argument?
In both cases it was argued that the removal by the Secretary of State under Regulation B13 of the Housing Benefit Regulations 2006 of part of their means-tested housing benefit in respect of their public sector housing was unlawful.
Judges heard that A's former partner has raped, assaulted and threatened to kill her, but she nevertheless faced losing £11.65 a week from her benefits as she was deemed to be "under-occupying her home.
The Department for Work and Pensions (DWP) argued that her challenge lacked credibility because discretionary housing payments were available through local councils to people facing exceptional circumstances.
The Rutherfords care for Warren, who has a rare genetic disorder which means he is unable to walk, talk or feed himself and is doubly incontinent.
The family live in a three-bedroom bungalow adapted for his needs, with the couple in one room, Warren in another, and the third needed for carers staying overnight and to store equipment.
They launched a judicial review over the regulations, which allow for an additional bedroom if the claimant or their partner require overnight care but make no provision for children who need an overnight carer.
How have the Rutherfords and 'A' reacted?
I'm a bit lost for words. I could almost cry with happiness. Other people are going to benefit from this decision as well. That was partly why we did it.
Our client's life is at risk and she is terrified. The anxiety caused by the bedroom tax and the uncertainty about this case has been huge. She is a vulnerable single parent who has been a victim of rape and assault. She is delighted that the Court of Appeal has recognised the impact that the bedroom tax is having on her and others like her.
What is likely to happen now?
The DWP is likely to appeal having been given permission to challenge the Court of Appeal's ruling at the Supreme Court.
A spokesperson for the DWP said: "We fundamentally disagree with the court's ruling on the ECHR (European Convention on Human Rights) which directly contradicts the High Court. We have already been granted permission to appeal to the Supreme Court.
"We know there will be people who need extra support. That is why we are giving local authorities over £870 million in extra funding over the next five years to help ensure people in difficult situations like these don't lose out."
We are delighted that disabled children will finally be entitled to the same treatment as disabled adults.