The gang from Birmingham pleaded guilty to terror charges at Woolwich Crown Court in relation to plotting the attack on the march in the West Yorkshire town of Dewsbury last June. They will be sentenced on June 6.
"Their capability was clear. They created devices that would have certainly maimed and possibly killed people depending on how close they were. Their intent was very, very clear. In my view they were very dangerous," Assistant Chief Constable of West Midlands Police Marcus Beale said after today's hearing.
Their plot, last summer, failed by sheer luck as the group turned up too late and the rally had already finished.
They were caught by another stroke of luck, as an error by one of the terrorists when taking out car insurance led to one of their vehicles being stopped by a traffic officer as they returned home.
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Prosecutors say five of the defendants travelled to the town to carry out the attack on the afternoon of June 30. A veteran traffic officer decided to stop one of their cars later on the motorway and found it did not have valid insurance.
The vehicle was impounded and when it was searched by staff at a compound two days later, they discovered a haul of deadly weapons.
The cache included two shotguns, ammunition, as well as an improvised explosive device packed with 458 pieces of metal shrapnel, including nails.
Although it remains unclear whether the terrorists planned to martyr themselves, the leaflet, which was addressed to the Queen and Prime Minister David Cameron, added that they "love death more than you love life."
All changed their pleas from not guilty on Tuesday via videolink, admitting preparing an act of terrorism between 1 May and 4 July 2012.