The BBC has heard from scores of victims from London and Essex who have shared stories similar to that of Maureen and Eric.
As part of an investigation, BBC London installed secret cameras at a vacant property while a BBC journalist posed as a customer who had locked their keys inside.
The BBC also asked Lloyd Morgan of the Master Locksmiths Association (MLA) to inspect the lock beforehand and to demonstrate how quickly it could be picked without the need for drilling.
“We should be able to bypass this lock in seconds, no damage whatsoever,” Morgan said.
Using just one tool he was able to open the door in seconds and said there were five methods that any trained locksmith could use to open our door without damaging the lock.
“An apprentice should be able to do this no problem,” he said.
Contacted by phone, 24/7 Locksmiths UK quoted £40 for “a simple door opening”.
But after one of their locksmiths arrived at the property, the cost increased tenfold within minutes.
“To open it I’m going to have to drill the lock because in the back of this you have a mechanism which is locking the door, so I need access to that mechanism,” he said.