Usury?

Approx 4 years ago I obtained a SAMS loan against my property with Barclays. At that time my home was valued at Ł92,500 and I obtained a Ł20,000 loan. Property in my area has escalated to the point where my home is now valued at Ł235,000. If I were to sell today at the valued price Barclays would get a total of Ł128,000 plus the original loan of Ł20,00. In short Barclays would realise over 500% over five years on a loan of Ł20,000.

I believe that this represents usury and Barclays are both legally (under an unfair contract) and morally responsible to review these contracts.