Violence

Possession - Section 8 and Section 21

Hi all, a good friend of mine who owns his home in a small residential street has some nuisance neighbours who live down the road in a privately rented home and apparently they are one of many idiot tenants that have rented this house, but things have taken a turn for the worse as my mate was severely beaten up by the tenant/neighbour in an unprovoked attack, my friend has CCTV and it was all captured so he (the tenant) was arrested etc, my question is can my pal ask or demand that the landlord of the property has this person evicted, I have told him to go to land registry and find out who owns the home and go to see them or write to them to try and have this now violent person evicted but I am not sure if the landlord has this power?
Any ideas?