A family member and her husband are renting a house from a friend, the landlord, and have only been living there about a month. There was no contract written up at all. They've become unhappy with the landlord and the house and wish to leave. The landlord is threatening legal action and claims there was a verbal agreement. He has said he will sue them for outstanding rent despite there being no terms - as there is no contract.
He has sent them the following:
"You have an assured shorthold tenancy agreement. The fact that there isn't a written contract doesn't change this as a verbal agreement is legally binding. Payment of rent constitutes acceptance of these terms. The tenancy can only be terminated early from the permission of the landlord. If you leave early this is legally abandonment and you are still responsible for paying rent for the duration of the tenancy ... if you do leave next month I'll consider you in rent arrears and pursue payment through legal means"
To me it seems the landlord has very little legal backing if they were to just leave. Can anyone with experience with UK renting shed any light on the legal reality of the situation?
EDIT
For futher information, I was mistaken in stating they had lived in the property for only a month, it has actually been just over 6 months. There were no witnesses to any verbal agreement, although there will most likely be a considerable number of text messages between the two parties, considering they are long time friends.