Do i have to pay this debt ?

Over seven years ago a debt was accrued without my knowledge within a previous relationship. Two debt collecting agencies have now hounded me over the phone for repayments. To be honest I wasn't in any frame of mind to think straight .... when you are told you owe �11,000 quid and they want it all back, it throws you a bit !! I felt threatened and believed their threats of court appearances and bankcruptcy. However, I have now been told that because its over seven years since the debt was were accrued i shouldn't pay. I would like to know if this is true. Furthermore if I do have to pay can they demand extortionate amounts, that as a self employed gardner I cannot afford to meet. Many thanks .....