Lawyer / Legal Advice Required

Recently taken over a small restaurant, takeaway, rent agreed @ 250 per week, and have been paying such amount for the ast 6 months. All of a sudden it has transpired that rent should be 290 pr week. None of the 3 lawyers (my lawyer, seller's lawyer, landlords lawyer) involved in the exchange process picked this up, and now it seems I'm left to pay the difference over the term of the lease. (for about 8 years left or so).

If I had known the rent would be that much, that would have swayed my decision to take over the premises. I don't know why the landlord has just all of a sudden picked this up. (Apparently there was an agreement that was set before the handover, that the previous owners were given some sort of concession, and t hat the moment the business was sold, that rent would go back up to 290 per week. At no stage in the process was this communicated to me. I've spoken with the landlord, and apparently, the piece of paper that he has, will protect him by law.

I need a lawyer/legal advice to take somebody (I don'tknow who) to court, as I'm now all of a sudden left with more money to pay per week on rent, which I don't think is fair.

I am in central London, in Islington.