Thank you for that. I saw the article previously. I have just had the below from another lawyer. Comments most welcome:
You could draw up a Deed of Variation varying your mother's Will so that your share was left on discretionary trust by her.
Alternatively, you could draw up a Deed of Variation varying your mother's Will so that you are deleted as a beneficiary and your share is left on discretionary trust to benefit your disabled child.
The rules as to deliberate depravation of capital are unclear. However, you have a greater chance of success if the trust is set up by a Deed of Variation rather than set up by you personally.
Also, I would consider that the arguments for setting up a discretionary trust for your disabled child is a stronger argument since you can state that one of the purposes of the trust is to manage money because your child will never have sufficient mental capacity to manage their own finances.
It appears that the only reason for setting up the discretionary trust for your own benefit would be to be able to still claim means tested benefits.
If the DWP did decide that this was a deliberate deprivation of capital, you can always appeal the decision to an independent benefits tribunal.
To answer your other questions:
1. If you receive your inheritance and then set up a discretionary trust fund, I consider that this would be seen as a deliberate deprivation of capital.
2. The best option would be to vary your mother's Will so that your inheritance passes direct to your disabled child with the Deed of Variation setting up the terms of the discretionary trust. I cannot guarantee that this would not be treated as a deliberate deprivation of capital but there are stronger arguments for saying that it is not.
The only person who needs to agree to the Deed of Variation is you. The other beneficiaries do not need to agree since it doesn't affect their share of the estate.
Decisions about deprivation of capital are down to the discretion of an individual decision maker.