Tenants in common: sale of property share by one co-tenant

I own my house with one other person as tenants in common. I wish to sell my share of the house. My prospective purchaser’s solicitor has told them that HMLR will not delete my name from the title and add the purchaser's name as a new tenant in common without the permission and signature of my existing co-tenant in common. Is this correct? I should add that my existing co-tenant in common has moved out of the property, has stated that they have no intention of returning, but refuses to engage with me in discussion of the sale of my share. 

If the house is jointly owned by yourself and one other person, both of you would need to be party to and execute a transfer of the legal estate in order to reflect any change of ownership.

Thank you for your reply. I think I understand now: I am able to sell my beneficial ownership share to another without permission of the other tenant in common, but as the legal ownership is held jointly by me and my current co-tenant then both of us would need to agree to a change of that.