ROYAL Mail tried to evict squatters who occupied its former delivery office in East Croydon in the week before last Saturday's illegal rave.
Royal Mail informed the police when squatters took over the building, which closed in March to make way for flats.
It is likely the squatters tipped-off the two "crews" that organised the rave during which 15-year-old Rio Andrew collapsed and later died in hospital.
Despite the Cherry Orchard Road site being patrolled by a security guard every three hours, those inside were able to bring in equipment using lorries and vans without making it obvious a large-scale event was about to happen.
When agents acting on behalf of Royal Mail did try to enter, they were met with physical threats and a security guard was injured.
Royal Mail then applied for a court order, but it was not granted in time for the squatters to be evicted.
On Monday, Royal Mail went back to court and secured emergency permission to remove the occupants.
A spokeswoman said: "All the squatters have now left the building and we have made the site as secure as we can to prevent any further unauthorised access.
"We are also accelerating our plans to demolish the building."
Police have admitted they were told about the rave more than a week before it happened but an intelligence officer reviewing the information decided not to act.
Croydon Central MP Gavin Barwell, who has criticised that decision, said: "The police mistake really costs when you consider Royal Mail's attempts to remove the squatters.
"The law is pretty soft on squatting so it normally takes time to get an eviction.
"Had they been able to say they had intelligence they were going to have a large illegal rave that weekend, the court might have taken a more urgent view on whether the squatters should be removed.
"They couldn't do that because the police didn't share that information with Royal Mail."
