A dutch teenager from Pinner stockpiled an 'arsenal' of weapons, ordered an Uzi sub-machine gun from the United States and kept the barrel of a high-powered AK47 assault rifle he intended to build under his mattress.

Former Nower Hill High School pupil Reza Khalilzada, 18, of Pembroke Avenue - on the Harrow-Hillingdon border - came to the attention of the authorities when US customs official X-rayed a parcel addressed to the young man and found it contained a IWI .22 calibre Uzi machine gun and 187 rounds of ammunition rather than the ceramic dish and the owl ornament the label suggested.

US Homeland Security Investigations notified the Metropolitan Police and officers from the London force's Central Task Force executed a search warrant at Khalilzada's address - where he lived with his parents and three siblings in a quiet cul-de-sac - six days later on August 14 last year.

Khalilzada told police he had responded to a website advert offering money to provide a 'drop-off address' for an unknown package because he was not doing well at college and wanted a job.

He claimed packaging for another heavy item delivered from the US that officers found in his garage had been for a camping chair in his bedroom - but the weight detailed on the packaging did not correspond with the weight of the chair.

Officers then uncovered the barrel of an AK-74 rifle under the mattress in his bedroom.

They also found a rucksack containing:

nunchucks

CS gas cannister

a lock knife

lighter fluid

aerosol cans

a lighter

a catapult and ball bearings

a scarf

a bandana

balaclavas

field dressing for wounds

bandage tape

amphetamines

ecstasy

four CDs containing images and videos of Khalilzada's family

Detectives seized ear defenders, three computers and a number of USB memory sticks, £600 in cash and several bank cards.

Khalilzada was charged with firearms offences on August 15 last year, the day after the raid.

The next day, his parents reported that another American-sourced package had been delivered for him.

It contained various parts of an assault rifle which, when combined with the rifle barrel found under the mattress, created a fully functional, automatic assault rifle with the potential to kill.

The ammunition seized at the US border would have fitted this rifle.

Examinations of Khalilzada's computer showed it was heavily encrypted. Khalilzada has refused to supply a password, which he claims he has forgotten.

The Observer has discovered that in 2011 Khalilzada won the 'Most Improved in ICT' award at a spring prize-giving at Nower Hilll High School in George V Avenue, Pinner.

Work is ongoing to decrypt the computer, which it is believed may contain key information about who Khalilzada ordered the firearms and component parts from.

Khalilzada pleaded guilty on December 3 last year at Isleworth Crown Court to two counts of possession of a prohibited weapon - regarding the AK-74 barrel and CS gas - and two counts of possession of a controlled drug, namely MDMA and amphetamine.

He pleaded not guilty to attempting to possess a prohibited weapon - the AK-74 component parts - and conspiracy to fraudulently evade a prohibition, for which he was found guilty on Tuesday January 28.

Detective Inspector Rob Murray, of the Central Task Force, said: "Khalilzada's arsenal contained everything one person would need to potentially kill and seriously injure a lot of people.

"With the assistance of our partners in the United States, we've taken these weapons off the streets and out of criminal hands, where they could have potentially resulted in very serious consequences.

"I hope this case and the sentence acts as a deterrent to anyone thinking of being involved in the illegal purchase or distribution of firearms and ammunition."

Matthew Etre, of the US Immigration and Customs Enforcement Homeland Security Investigations Attaché in London, said: "This case is an example of Homeland Security Investigations' commitment to investigate and help disrupt the flow of weapons and sensitive technologies illegally exported from the United States.

"HSI special agents will continue to work in collaboration with our law enforcement partners in the United Kingdom to keep the citizens of both our countries safe and secure."

Khalilzada received six concurrent jail terms totalling six years on Friday.