In this ACAS leaflet
http://www.acas.org.uk/CHttpHandler.ashx?id=30 6&p=0
it says, "The legal position
Employers are responsible for preventing bullying and harassing
behaviour. It is in their interests to make it clear to everyone that such
behaviour will not be tolerated � the costs to the business may include
poor employee relations, low morale, inefficiency and potentially the loss
of staff. An organisational statement to all staff about the standards of
behaviour expected can make it easier for all individuals to be fully aware
of their responsibilities to others."
It seems like your boss is your employer (if there is no one above them). Therefore they are not doing anything to prevent it! It might be worth giving ACAS a call and outlining the whole situation.
Hope you get it sorted