Marian - many thanks and they were the ones who applied and were advised as stated. SM applied for the restriction using the form RX1 and submitted a copy of the death certificate as well. The key to updating the register re a death is that the required evidence is provided. If a random individual applied, so not the other joint owner or a conveyancer, we would carry out wider checks as appropriate for example serving notice on the surviving owner.
Having a charge on the title is not necessary here as the restriction applied for is sufficient protection of any interest. If you are challenging the application made/the restriction applied for and registered I would strongly recommend seeking legal advice The alternative is to apply to cancel the restriction using form RX3 and providing supporting evidence to enable cancellation
Notices, restrictions and protection of third-party interests (PG19) - GOV.UK