By law, your landlord is required to protect your deposit within 30 days of them receiving it. This is to stop landlords from using the deposit as their own income and to ensure that the deposit is protected when your tenancy is over.
If they fail to protect your tenancy deposit, they are liable to a penalty of between 1-3 times the amount of the deposit paid. If you have renewed your tenancy agreement and there is more than one breach, the penalty could be much larger.
Even if your landlord protected your deposit but failed to inform you where your deposit was registered within 30 days, you may be entitled to compensation