These appeals are brought on behalf of various lone parent mothers and their young children to challenge the legislative provisions known as the benefit cap. These provisions originally capped specified welfare benefits at a total of 26,000 per household. But by the Welfare Reform and Work Act 2016 the government and Parliament reduced the cap to 23,000 for a household in London, 20,000 elsewhere. Single people (including lone parents) are exempt from the revised cap (the cap) if they work for 16 hours each week. The aim of the cap is to incentivise work. The appellants argue that in introducing the cap, the government, through Parliament, has discriminated against lone parents of young children, whose childcare obligations severely curtail their ability to work, and against the children themselves. In the DA case the appellants are three lone parent mothers two of whom had a child under two at the outset of proceedings, and those two children themselves. In DS, the appellants are two lone parent mothers with nine children, three of whom were under five, and those nine children themselves. On 22 June 2017 the High Court held in the DA case that the benefit cap unlawfully discriminated against the children under two and their mothers, but on 15 March 2018 the Court of Appeal set aside the High Courts order. On 26 March 2018 Lang J formally dismissed the DS claimants claims but granted a leap frog certificate so that they could apply to appeal directly to the Supreme Court. The Supreme Court dismisses the appeal by a majority of 5 2. Lord Wilson (with whom Lord Hodge agrees) gives the main judgment. Lord Carnwath (with whom Lord Reed and Lord Hughes agree) and Lord Hodge (with whom Lord Hughes agrees) give concurring judgments. Lady Hale agrees with Lord Wilson on the principles, but not the outcome. Lord Kerr disagrees with him about both. Lord Wilson acknowledges that the cap has had a major impact on lone parent households with a child aged under five and in particular under two [22]. It does incentivise them to try to find work for at least 16 hours per week, but this was argued to fly in the face of the governments own policy of providing no free childcare for children under two and of replacing income support with job seekers allowance only after a lone parents youngest child has reached school age. The governments funding of Discretionary Housing Payments (DHPs) may alleviate the impact of the cap on such lone parent households but the evidence on this could be stronger. The cap saves little public money, but it can take the families it affects well below the poverty line. Living in poverty has a particularly adverse impact on the development of children under five [23] [34]. The caps reduction of benefits to well below the poverty line engages the claimant mothers and childrens right under Article 8 of the European Convention on Human Rights (ECHR) to respect for their family life [35] [37]. Each of the four classes of claimants has a separate status under Article 14 (for example, lone parents of children under two) on grounds of which status, they might complain they face discrimination in the enjoyment of that right [38] [39]. Their complaint, for which there is prima facie evidence, would be that despite being in a relevantly different situation from others subjected to the cap, they are treated the same way see Thlimmenos v Greece (2000) 31 EHRR 12 [40] [51]. The government must objectively justify this discrimination in this case, its failure to exempt the DA and DS cohorts from the cap [52] [54]. The test for whether the government can justify a discriminatory rule governing the distribution of welfare benefits is whether the rule is manifestly without reasonable foundation (MWRF). Once the government has put forward a foundation, the court will proactively examine whether it is reasonable [55] [66]. The United Nations Convention on the Rights of the Child (UNCRC) requires the public authorities to treat the childs best interests as a primary consideration. It forms no part of our domestic law, but aids interpretation of the ECHR, as to whether the government unjustifiably discriminated against the children and their parents in their enjoyment of their right under Article 8. The evidence shows that the government did, as a primary consideration, evaluate the likely impact of the cap on lone parents with young children [67] [87]. Furthermore, the governments belief that there are better long term outcomes for children in households where an adult works is a reasonable foundation for treating the DA and DS cohorts similarly to all others subjected to the cap [88]. Lord Carnwath and Lord Hodge both express reservations on the issue of status, but agree with Lord Wilson on the relevance of the UNCRC and also on the application of the MWRF test. They agree with him that the executive and Parliament both gave proper consideration to the interests of the children affected [89] [123], [124] [131]. Lady Hale agrees with Lord Wilson on the legal principles but not their application. She holds that the government failed to strike a fair balance between the very limited public benefits of the cap and the severe damage done to the family lives of young children and their lone parents if the parents must choose between working outside the home and not having enough for the family to live on [132] [157]. Lord Kerr considers the MWRF test to have derived from the margin of appreciation which is afforded to decisions of national authorities in the European Court of Human Rights. He would not import this approach into the national courts consideration of a measures proportionality. The steps in the proportionality analysis at the national level are well settled in the case law [164] [172]. The MWRF standard should not be applied as part of this analysis instead, the question should be whether the government has established that there is a reasonable foundation for its conclusion that a fair balance has been struck [173] [177]. In relation to the UNCRC, Lord Kerr does not agree with Lord Wilson that the key question is whether the government has acted in breach of Article 3 of the UNCRC [183]. A finding that Article 3 has not been breached does not establish the proportionality of the measure [186]. The evidence in this case shows that, while the impact on childrens rights was considered, it was not given a primacy of importance which Article 3 requires [196].