In Newham there are now 25,000 landlords and increasing numbers are exploiting the system and their tenants.
Early morning raids are designed to find the evidence needed to prosecute.
Kudirat Ojelade lives with her children in just one room. She is one of nine mothers in one of nine cramped bedsits in this house. This is the best she can find.
Downstairs in the basement they discover a room with one blocked up window it makes the landlord £520 pounds a month.
The property is suspected of breaching regulations. Officers interview innocent tenants to build a case.
These families have come from other boroughs they have no where else to turn, stuck here until alternative accommodation is found.
We moved on - travelling with the police - to a second home which we were warned would be dangerous.
The owner of this property is currently being prosecuted for renting it out to a family unlicensed and severely dilapidated.
Despite that police and council enforcement officers suspect the landlord of once again letting it out.
It's clear to see no improvements have been made the house is falling down. It's a hazard to the couple who now live here.
There's a bath in what should be the kitchen, the room is damp and there are electrical appliances everywhere.
The third house is unlicensed and home to eight people. Damp and mouldy with children living in squalor.
The landlord being paid an estimated £2,500-a-month. For these private tenants - the future is bleak.
Once the property owner is prosecuted they'll have to move on.
In Newham unlike anywhere else in the country all rented property must be licensed to curb the rise of rogue landlords.
A challenge considering now nearly half of all homes are rented out.