Spanish police met mob chiefs every four weeks for instructions
The Kinahan cartel was paying two Spanish police officers €5,000 a month at the time of the Operation Shovel investigation.
A multinational operation, it saw around 30 cartel associates arrested in Spain, Ireland and the UK in 2010.
The two officers were on the mob's payroll to keep them informed of any investigations into their activities on the Costa del Sol.
They were met by a senior cartel lieutenant every four weeks in one of the many obstructions to the high-profile Spanish investigation into their activities.
Shovel was hailed by Spanish police as the "end of the Irish Mafia'", but 10 years after the massive clampdown, Christy Kinahan and his sons Daniel and Christopher Jr are still free.
It emerged last week that the Spanish authorities have levelled a charge against Christy Snr for passport fraud and a weapons charge on CAB target Ross Browning.
State prosecutors dropped the case against a string of other suspects, including Daniel and Christopher Jr, after failing to build a case over 10 years.
At the weekend, the Sunday World revealed the catalogue of failures by Spanish authorities that gave the Kinahan gang free rein to continue to expand its drugs empire.
The mob was always one step ahead of the Spanish police and knew cops had them under surveillance and were moving in.
Tip-offs provided by paid informants allowed them to tidy up their affairs and leave behind a trail of documents.
They knew these would not only be found in the raids but would also tie up investigators for years and come to nothing.
They included details of a company selling land in Brazil, where it was claimed the Kinahan gang was planning to build a holiday resort near the coastal city of Joao Pessoa in the north-east of the country.
Huge resources were pumped into untangling the financial web of Greenland Securities.
In the end, investigators discovered the land was barren and the mainly elderly investors had been left in a legal tangle with Brazilian authorities to try to claim ownership of the plots.
After two years of surveillance, Spanish police led the charge against the mob in May 2010.
The busts had involved 750 police officers across Ireland, the UK and Spain, as well as follow-up raids in Belgium, Cyprus, Dubai, South Africa and Brazil. They resulted in 78 searches, 34 arrests and the seizure of vehicles and cash.
Europol, the EU police agency at the time, said Christy Kinahan's network was involved in financial aff-airs in South America, Africa and the Far East. Thirty-one companies linked to the Kinahan gang were identified.
Daniel and Christopher Jr were publicly dragged before the courts along with long-time associate John 'The Colonel' Cunningham.
Mob lieutenants Gary Hutch and Freddie Thompson faced extradition proceedings, while armed robber Kevin Lynch and others were bailed in Spain.
Accountants, solicitors and associates of 'Dapper Don' Christy were also named in the probe. The arrests were filmed by the Guardia Civil and shown by the world's media, but it was later discovered the gang had been tipped-off.
The Kinahans were locked up but were later granted bail by a Spanish magistrate.
In its early stages, Operation Shovel promised it would destroy the "Irish mafia" and concentrated on allegations of drugs and weapons trafficking.
By 2014, a magistrate dropped those charges and decided to focus on money laundering and membership of a criminal gang. Six years on, those charges were also dropped.
The charges last week were welcomed as "more than was expected" out of the doomed investigation, which fell further down the Spanish police's priority list the more difficult it became.