Counter terrorism officers had EDL attack plotter Jewel Uddin under surveillance for nine months before his arrest because of his links to other extremist groups.
Uddin was linked to the 11-man Birmingham terror cell jailed last week for plotting to detonate bombs across the UK.
He regularly played football with members of the terror cell led by Irfan Naseer and Irfan Khalid, who were secretly taped by police promising 'another 9/11'.
He had met up with Naseer's gang just before police swooped in September 2011, but was not directly linked to their bomb plot. Marcus Beale, in charge of counter terrorism for West Midlands Police, said there was no evidence that Uddin had started building his own terror cell.
"With the best information we had, we couldn't have done anything differently', he said. 'We have looked at it and there weren't the dots to be joined."
A search of an impounded car, stopped by a traffic officer on the M1, revealed a cache of weapons belonging to the gang who planned to attack an EDL march in Dewsbury, West Yorkshire.
There were also 10 copies of a hate-filled note addressed to the enemies of Islam, the Queen and Prime Minister David Cameron.
It said: "This is a message to the enemies of Allah and his messenger. This is a message to the kafir (non-believer) female devil and self-proclaimed Queen Elizabeth and her accursed jubilee, fooling a nation of blind sheep to your self-proclaimed royalty and majesty."
The document addressed the EDL directly, saying: "To the EDL (English Drunkards League). O enemies of Allah! We have heard and seen you openly insulting the final Messenger of Allah... you should know that for every action there is a reaction.
"Today is a day of retaliation (especially) for your blasphemy of Allah and his Messenger Muhammad. We love death more than you love life. The penalty for blasphemy of Allah and his Messenger Muhammad is death.
West Midlands Police have released video footage taken from a police traffic officer car following the stopping of the Renault Laguna containing Omar Khan and Jewel Uddin (in the white cap.)
The video also shows police helicopter shots of the EDL Dewsbury rally.
The gang who plotted to attack an EDL rally in Dewsbury were well armed and intended to kill, according to Assistant Chief Constable Marcus Beale from West Midlands Police.
He said the fact that they were caught was a testament to one traffic officer, who had just as much part to play in anti-terrorism as any specialist.
A search of a car that was impounded after two members of a conspiracy to attack an EDL rally in West Yorkshire were pulled over, found an arsenal of weapons.
Two shotguns, swords, knives, a nail bomb containing 458 pieces of shrapnel, and a partially assembled pipe bomb were discovered.
The nail bomb was an 18-inch (46cm) long rocket which had been stuffed with shrapnel and was to be powered by explosives taken from at least two large fireworks.
Six men have admitted plotting to attack an English Defence League rally in Dewsbury, West Yorkshire, last June.
Omar Khan, Mohammed Khan, Mohammed Hasseen, Anzal Hussain, Mohammed Saud, Zohaib Ahmed and Jewel Uddin admitted preparing an act of terrorism between May 1 and July 4.
A failed attack on an EDL rally last year was only uncovered because a traffic officer stopped two Islamic extremists on the M1 as they travelled back to Birmingham.
He made checks on their Renault Laguna, which came up as being uninsured, and the car was impounded.
Two days later staff at the pound near Sheffield looked at the contents of the Renault and found the gang's deadly arsenal.
A plan by Islamic extremists to target the English Defence League fell apart because the gathering in Dewsbury, West Yorkshire, finished earlier than expected.
Police and security services had no intelligence about the planned attack on June 30 last year, although one of the would-be killers was under surveillance in relation to another terrorist plan.