Severing joint Tenancy

[Hagalout]

My mother severed the joint tenancy of the property she shared with her partner 15 years ago, they have both passed away but it seems the severance was never registered on the title deeds at the land registry. She signed the basic document but apparently none of the other required form's were ever sent to the land registry and it still shows as them being joint tenants. My original solicitor who's company supposedly did the transaction, said that the paper my mother signed has legal standing but my current solicitor gives conflicting advice. I need to know where I stand if anyone can help. Thanks.

[atticus]

Your original solicitor is probably right, provided that (i) the severance was by mutual agreement (did they both sign the document?) or (ii) your mother served notice of severance on her partner. Registration at Land Registry is advisable but not necessary to complete the severance.

If the joint tenancy was severed, the partner's interest in the property is vested in his estate.

[Hagalout]

Thanks Atticus.
No, they didn't both sign the document and I couldn't be sure if she served notice on him to be honest. They lived together obviously but he was in the early stages of dementia and I think my mum was advised to go down that route. Her will states that they owned the property as Tenants in Common but his will doesn't mention it.