deposit management

Tenancy Deposits

Please ponder on this scenario:

10 April -  prospective tenant voluntarily gives 1 week holding deposit to the landlord and reference process commences.

24 April - a fortnight has lapsed however the reference process still hasn't completed.  It takes longer than usual to gather the documents.  At this point the tenant voluntarily gives 4 more weeks of deposit to the landlord, in the hope of showing his sincerity in renting the property

1 May - the result of the referencing process turns out that the tenant fails to satisfy the critieria.  

Can the landlord keeps the 5 weeks deposit without returning it to the prospective tenant as a result of wasting the landlord too much time and energy, and opportunity cost?