If the tenant is using the rented accommodation for anti-social activities, then Landlord would have to 4 weeks notice to the tenant for leaving.
In the UK, the exchange of sexual services for money is legal, but a number of activities, including soliciting in a public place, owning or managing a brothel, pimping and pandering, are considered to be crimes, under the Sexual Offences Act 2003.
Your tenant can get in trouble if he is caught soliciting for sex in a public .
I would not suggest you to collect evidence yourself, rather to report it to the police, so that they can ask him to stop such activities.
I hope this helps.
If you need further assistance, please let me know.
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