All your friend needs to do is make contact with her local police station either by phone or in person, ask to speak to an officer who is experienced in domestic violence, and be honest about what he is doing, the physical, verbal,and other abuse she has sustained, and continues to sustain, past and present injuries etc.
If he is not named on your friend's mortgage/deeds/tenancy agreement, he has no legal right to remain in her home if she doesn't want him there and she can call the police and asked for him to be removed from her property at any time of the day or night.
I suggest that, if she feels that she cannot dial 999 when he is screaming at her etc, she asks her neighbours to do so - in fact, it seems surprising that none have taken the initiative when they've heard her being abused.
As for him taking revenge if he's forcibly removed from her home, many bullies rely on bluff and bluster and it's probable that an encounter with the boys/girls in blue will be sufficient to persuade him that he's best advised to leave her alone.
If not, an easily obtained non-molestation/restraining order will prohibit him coming within a set distance of her/her home, but once he's been arrested and cooled his heels in the cells a couple of times it's likely he'll see the light and move on to a new victim.
Does your friend have dc? Regardless, your friend needs to act sooner rather than later as far too many women have ended up sustaining serious injury, and worse, because they believed it couldn't happen to them - Tina Nash being one such example of misguided thinking.
Fortunately, Tina lived to tell the tale but many other victims of domestic violence haven't.
Your friend's self-esteem will be in bits; does she have access to a computer? Can you refer her to this board so that she can be reassured she is not alone in having placed her trust in a man who subsequently revealed himself to be nothing more than a vicious bully?