Unfortunatley Camden Council is absolutely hopeless when it comes to dealing with anti-social residents, which are often just moved from one estate to another. Inaction by the Council is a clear breach of their landlord responsibilities towards tenants and leaseholders, who have a right to a quiet enjoyment of their flats. From experience, the standard response from Camden Council officers is “call mobile security patrol” or “dial 101”.
Apart from raising a formal complaint I would get in touch with your Ward Councillor ( http://democracy.camden.gov.uk/mgFindMember.aspx ). I would tell the councillor that your reports of ASB have been repeatedly ignored by the Council, and I would ask the him/her to get the Council to take immediate action against their anti-social tenant. I would not call the Mobile Security Patrol, because for every call-out you will be charged in your service charge bill. In effect you are paying for the Council not assuming its obligations as the landlord and freeholder. Rather call 101 (non-emergency police).