No death registered of first joint tenant before second joint tenants death

My parents are currently registered as joint tenants to their property. Mum passed away in 2022 and dad passed away in 2025. Neither death has been reported to the Land Registry as yet. I am one of four beneficiaries in my dads will and I am also the executor of my dads will. I have been granted probate. We intend to sell the house within six months. 
Is it a requirement that I have to register both deaths before the sale of the house or is it more efficient for the conveyancer of the sale to deal with the registration of the transfer to the new owner during the sale process please?

If it is a requirement of the executor (me) to register the death of the last owner (dad), before the sale, do I need to register mum's death first?
I originally intended to use form DJP to first register mum's death; however, form DJP states that this form is only to be used where there are remaining/surviving registered proprietors and dad has passed away.

If you would be kind enough to advise me of the process that the Land Registry requires please it would be appreciated.

Michael - sorry to read of your losses. A buyer can usually rely on a copy of the register, your Mum's death certificate and your Dad's probate in order to complete their purchase. It is rarely necessary to update the register as a result re both or even one of the deaths

I'm in a similar position. Does the same apply to owners of a freehold with 'title absolute'? Some websites say that we need to complete a DJP form for Mum first, but the form implies it's not the right one to use in this situation.

Matt - same advice. The type of tenure (freehold/leasehold) and class of title (absolute /possessory) has no impact on the advice

Thanks Adam.