Harassment

The legal definition of harassment is when a landlord or landlord's agent:

carries out acts which are likely to interfere with the peace and comfort of an occupier
persistently withdraws or withholds services required by the occupier

It is an offence for a landlord to carry out the above acts if it causes the occupier to leave or stop them from exercising their rights to the property, eg if the landlord cuts off the electricity supply.

Harassment can take many forms, if proven, the following may be a criminal offence:

disconnection of essential services such as electricity, gas or water
removal of or interference with occupier's belongings
preventing access to bathroom, kitchen or garden to which the occupier has shared or exclusive right
entering an occupier's home without consent
making threats to persuade an occupier to leave.