If there is a black and white clause written you are to pay for the full tenancy, there is no easy solution.

It is an expensive mistake not to read through the draft of the TA when presented to you. The law will always uphold this clause and he can easily sue you.

Best solution, speak nicely to the owner for a settlement. If the owner is a hardnut, bad luck. Or just as he said, find a tenant to replace your business.

Good luck