Modifying deed of trust (trust of land)

[potrzebie]

A & B (husband & wife) are hold title jointly to a buy-to-let London flat.
A,C,D,E & F (A & her children) hold beneficial title under a Trust Deed.
A dies.
Ignore mortgagee, HMRC and Land Registry issues. B & C are executors under A's will, not yet submitted for probate. Mortgage will be paid off from other funds of C,D,E & F before A is removed from title (Form DJP) and C added to title (Form AP1).
Question: How does the Trust Deed get modified?
Land Registry guidance ("1.2 Beneficial joint tenants") is obscure. I'm headed to UCL Law Library but maybe the answer is obvious.

[theycantdothat]

The trust deed should not need modifying. If the beneficiaries hold as joint tenants then A simply drops out of the picture. If they hold in some other capacity then (a) if the trust deed does not say what happens to A's share it passes under her will (b) if it does say what happens then that is what happens.

[atticus]

A new trust deed between the surviving owners of the beneficial interest may simplify matters.

[dls]

The deed of trust needs to be looked at as to the manor of appointment of a second trustee of the legal estate. One has to be appointed to achieve a sale.

The trusteeship is not part of A's estate, and A's executors have no standing as executors.