Commercial lease

[Nema]

I have a lease which on the head of terms stated a 5 year break clause. However the lease omitted any break clause which was missed by my solicitor. I had no idea the head of terms were not part of the lease and gave 6 months notice. The landlord refused to accept this notice as he said no break clause existed in the lease. If I take this further am I likely to get out of my lease. On the case of taking up a negligence claim with the solicitor that drew up the lease, what kind of result is this likely to have.