@moneyisnotfunny
This is how it would be handled in the US, but obvs may not apply in the UK. If I were you I'd get legal advice.
Situation: Child receives inheritance/cash gift, parent is on 'benefits' (aka 'Welfare' in the US)
The bequest would be put in a trust in the child's name with a third party trustee (usually a lawyer, banker, or trusted relative/friend). This is to show that the child is the 'owner' of the money and the parent has no direct access to it. The trustee disburses funds for the child's needs directly to the provider (school fees, medical needs, bills for clothing etc). Funds as above disbursed to the parent directly 'for the benefit of the child' must be accounted for with a paper trail. In some States a pro rata share of household expenses can be sent to the 'householder' to cover the child's 'food and shelter' and is excluded as income to the parent. In other States, it is counted as income and deducted in full or in part from the parents Welfare benefit. In the US, each state makes its own rules.
One thing, since there is no actual will, unless this actually goes through the courts as an 'Estate Intestate', this might not legally be classed as an inheritance. So if, for instance, that money was in a joint account with another person (ie the deceased's spouse or parent) the 'ownership' would belong to the other account holder and the money would be considered a 'gift', not an inheritance.
Again, I know the UK benefits and legal systems may operate under different rules, but I've found them similar in many instances. This may just give you a 'guideline' to ask about when you see a solicitor.
Edited to add; the above usually applies to LARGE sums of money, not to small bequests.