The trio were arrested a year ago after security services bugged one of the men's cars, as well as uncovering a pipe bomb and a meat cleaver hidden in a JD Sports bag.
However, a jury at the Old Bailey today found all three guilty of preparing for acts of terrorism, at the end of a lengthy trial.
Jurors at London's Central Criminal Court on Wednesday found Naweed Ali, Khobaib Hussain and Mohibur Rahman guilty of preparing terrorist acts, after a trial that was partly held in secret for national security reasons.
They had collected a small arsenal including a half-made pipe bomb and a meat cleaver with the word "Kafir" etched into the blade, and used a Musketeers image from the Disney cartoon movie as a logo on encrypted Telegram messages.
Both Ali and Hussain had previously been jailed for terrorism offences after they tried to join an Al Qaeda training camp in Pakistan in 2012, the BBC reported.
The trial heard how a meat cleaver with the word "KAFIR" - Arabic for non-believer or infidel - scratched on to the metal blade was found in a vehicle used by Ali.
Other items included an air pistol imitation hand gun with an empty magazine taped to the side of it, 11 more shotgun cartridges, a live unfired 9mm bullet, a roll of gaffer tape and a pair of black latex gloves.
As they arranged an assault, the men were under reconnaissance by Britain's residential knowledge benefit, MI5, which made a fake dispatch organization in the focal England city of Birmingham and enlisted Hussein and Ali.
Ali, Hussain and Rahman met while serving prison terms for terrorism offenses, prosecutors said.
A fourth respondent, Tahir Aziz, was sentenced a similar charge.
Sue Hemming, the head of the counter-terrorism division at the Crown Prosecution Service (CPS), said: "The prosecution was able to show that these men shared the same radical belief in violent jihad and had reached a stage where they were planning to take action". The judge rejected one member of the jury, however enabled the trial to proceed.
The men were caught when one of them turned up for his first day at the...
The five-month trial at the Old Bailey nearly collapsed when a juror joked about being attracted to the officer in the case.
Counter-terror police also found shotgun shells, a bullet and an imitation handgun inside of Ali's vehicle, According to the Independent.
Ali told the court he was only interested in "innocent pasttimes" such as playing Federation Internationale de Football Association on his Playstation and watching the USA sitcom "The Big Bang Theory" on TV.