Its possible that the landlord is under pressure himself, but that's no excuse for the attidtude he is taking.
According to sunday tribune today traders in the top shopping centres are banding together and refusing to pay rents unless landlords agree to reductions. - Liffe Valley, Pavilions, Mahon Point cork etc.
Technically there is nothing in a lease that allows a reduction or for you to walk away, but current market conditions have made renegotiation a lot easier.
It may be a case of telling the landlord that you will have no option but to close the company if he does not negotiate as continuance of the high rent wouild put you in a position of insolvent trading - Put all correspondance in writing.