As a landlord I don't care how much your lease has increased since inception. I think your only bargaining chip is to find another space, preferably nearby. If the space is better and cheaper then you have to notify your landlord that you are interested in moving to a new location and that you would like to break your lease. See what the response is. If it is no way, ask if you can sublet. If the answer is still no, then see whether he will renew your lease now with new terms, to be negotiated. A new 10 year lease is more valuable to your landlord even at a lower psf than a high value 3 yr lease that everyone knows will not be renewed.
If the landlord says that he would be happy for you to break your lease and leave you have to decide what to do next. Leave or ask if he is interested in renegotiating the terms of your lease to stay.
Good luck. There is no easy way to do it. Sometimes a broker can help, if you find the right one.
Nov 4, 2008