Unmarried Partner Visa

Good Afternoon,
I need advise for my Close Friend.
He was married to person and separated 2.5 years ago. He is British Citizen and his ex-wife is in abroad(Not British National).
Both Parties are not coming on point where they can settle this matter. They both are not divorced yet.

He has found someone from last 1.5 year and in relation with her (non-married). We would Like to know is there any way he can apply Unmarried Partner visa for her (she is in abroad as well).... As per the situation it look like they will never settle down this matter because of ego.

Thanks in Advance.

An unmarried partner visa has a mandatory requirment to submit substantial documentary evidence proving they have lived together in a relationship along to marriage for at least 2 years. It seems they cannot prove this.