British special forces had built up a detailed intelligence picture of Islamic State’s command structure and were hoping it would lead them to the captured Brits.
But the plan collapsed after one of IS’ command and control centres was destroyed by the war planes.
Spooks had been monitoring mobile phones used by the senior members of the terror group.
The British spy agency GCHQ, right, had also intercepted emails and texts sent between terrorist leaders and was hoping to pinpoint the location of the hostages.
“After the US bombed the communication centre the plan fell apart”
Intelligence experts and the SAS were trying to build a “grid” showing the precise location of all known IS leaders in Iraq and Syria.
Sources say the grid amounted to “pins on a map” showing where the senior commanders were based.
GCHQ analysts were also trying to work out whether the hostages were at the same locations as the IS high command.
A source said when the US jets attacked, special forces were still trying to establish the whereabouts of British hostages Alan Henning and David Haines – who were both beheaded – and captive John Cantlie, who was kidnapped in 2012 and is still missing.
The raid knocked out the mobile phone network for several days and the leaders being targeted by the SAS disappeared.
An intelligence source told us: “GCHQ can hack into any mobile phone conversation anywhere in the world.
“They can target different individuals over the internet or by mobile phone calls.
“Target lists were being drawn up and a grid of senior IS leaders was being established.
“It was the basic intelligence needed to mount a rescue mission.
“But after the US bombed the communication centre the plan fell apart.”
Meanwhile, an SAS source has told the Daily Star Sunday our Government should have negotiated with IS and paid a ransom to save the British hostages.
The insider said that, although the Government does not officially pay ransoms, payments have been made before.
The source said: “You have to negotiate with kidnappers if you want to get hostages out.
“A government which refuses to talk is basically giving the hostage a death sentence.
“All hostages that have been released in the last few months, either from IS or other terrorist organisations, had their ransoms paid.
“Terrorists don’t release hostages through the goodness of their hearts.”
The source said that, while the Government won’t pay, there is nothing to stop security companies specialising in kidnap and ransom doing so.
The source added: “The big question which needs to be asked is why wasn’t a private kidnap and ransom company used to negotiate with the terrorists when it has been done before?”