Good afternoon Jolly
I'm afraid that this is correct.
Your liability will depend on whether the lease is a "new lease" (one granted after 1 January 1996") or an "old lease" (one granted before 1 January 1996).
If you assign a new lease, you should ensure that your solicitors include a condition of that the tenant enters into an "Authorised Guarantee Agreement" (an AGA). This is effectively a guarantee to the Landlord that the new tenant will pay the rent and perform the covenants in the lease for the remainder of the term and a promise that if it does not
do so, the old tenant will. A properly drafted AGA will limit this guarantee to the period of the new tenant's occupation. Should the new tenant assign the lease to a third party then the your liability comes to an end. If the new tenant does not pay its rent, the landlord can make a claim against you under the AGA.
The original tenant of an old lease is liable to pay the rent and perform all the covenants in the lease for the entirety of the term and, in some cases, any extension to that term.
That is the simple answer and your solicitors will explain it more fully if you require it.
I hope that this answers your question. If so, I would ask you, please to click 'Accept' so that I can be paid. If you require clarification, please don't hesitate to ask.