OP
The Ghost
I would contact the police and raise a complaint bringing it to the attention of the duty sargeant. If this produces no results I would escalate it to my local councillor. This make me quite angry that police are not moving to protect citizens from serious harm as is their duty. You can sue the police where they have failed to meet their duty and harm has resulted. You need to keep a log of events. When contacting the police or landlords you should also advise them of your intention to invole your councillor in the absence of a satisfactory resolution. You might also enlist the support of other tenants who have been bothered by this person. The way the polic work is that they will rarely intervene if just one person complains they want more people to make a complaint and then they will act.