Tenant has no lease, paying no rent and refusing to leave my premises

[Guest]

Im a landlord of a commercial property in Liverpool. My current tenant has been in the property for around 15 years. He originally had a lease in his first limited company name back 15 years ago. After around 7 years he dissolved his company and created a new limited company and carried on trading without a lease. He had some difficulties at home so the rent began to come in bits and bobs. I asked him around 2-3 years ago if he would like a new lease and he would have to stick to paying full rent and on time but he refused. He basically operated as a caretaker to the building as he said he didn't want to carry the business on. I have found a new tenant and agreed terms for them to take over beginning of this month but my current tenant is now refusing to leave. I have now found out the current tenant has dissolved his second limited company and opened a new one in July 18 with a business partner ( I think he has bought into the business ). They are now saying they have security of tenure which I think is wrong as for 1 they have no lease and 2 its a new company formed without my knowing. Any advice on this would be much appreciated as I feel he is using my kindness for weakness along with my age! Thank you.