Selling half a house?

here's a weird one for those in the know of house sale legalities..

a friend and her partner bought a property here in 2006, , due to a disagreeable seperation and his need to pay off a debt.. he is trying to sell his 50% to strangers.. he has even found 2 people prepared to buy into this deal.. and is convinced he can achieve a sale like this..

does anyone know if such a deal is possible... aside from being totally amoral, vindictive and stupid towards his ex..

she has visited a notaire, and he says it is not possible.. but it would be re-assuring for her to hear from a wider audience who may have other knowledge..

thank you for your reply Debra, i've been waiting to see what a notaire has had to say about the viability of any sale going ahead.. The notaire had initailly said it was possible, the retracted his statement a week later saying he made a grave mistake and it is not possible..

Today, 27th October, the other party proposing to sell his share has emailed my friend and is totally adamant he can and will sell his share and the buyers are due in France early November to see thier notaire and make arrangements for the transaction..

He's dilusional, bulls***ing, or knows something everyone else is missing?

I have strongly recommended my friend visits another well know local notaire with many years experience of conveyancing.. for a second opinion.. and to have what he says written and signed.