The relationship between a landlord and tenant is fundamentally based upon trust. The landlord trusts that you will take care of his property and that you will pay your rent in full and on time. The tenant trusts that the landlord will take care of the property and his deposit as required by law.
Essentially the landlord agrees to keep the tenants deposit safe until such time as the tenancy ends and the tenant moves out. Subject to any reasonable deductions for rent arrears, repairs, damage and missing inventory. However, many landlords find all sorts of reasons to deduct money from the deposit when the tenant moves out. Very often Tenants leave without getting a sniff of the money they had left in trust with the landlord. Leaving tenants with the short end of the stick. Feeling that they have very little recourse to justice.
To deal with this problem, the Housing Act 2004 incorporated the tenancy deposit scheme. Making it a breach of the law when a private landlord of an assured shorthold tenancy (after April 2007) fails to secure the tenancy deposit with an authorised deposit protection agency within 30-days of receipt and or when the landlord fails to inform the tenant or person paying the deposit of the details of the protection agency and as to how the deposit can be claimed at the end of the tenancy.