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Australians and New Zealanders wait overnight for the Spirit of Place Ceremony and Dawn Service at the ANZAC Commemorative ServiceTristan Fewings/Getty Images

A UK court has heard how a terror plot by a Blackburn teenager would have "in all probability" caused a number of deaths if it had not been foiled by security services. The 15-year-old, who cannot be named for legal reasons, plotted to attack an Anzac Day parade in Australia in April.

At a sentencing hearing held on Thursday (1 October), Manchester Crown Court was told how the boy incited terrorism by encouraging a Melbourne man to behead police officers. The Lancashire teen, who has pleaded guilty to one count of inciting terrorism, is thought to be the youngest Briton guilty of a terror offence.

Prosecutor Paul Greaney QC told the court that the boy, who was dangerously radicalised, had been viewing Islamic State (IS) propaganda online as he plotted the acts of terror "from the bedroom of his parents' suburban home". He said the defendant, then aged 14, had sent thousands of online messages to 18-year-old Australian suspect Sevdet Besim, including one encouraging him to "break into someone's house and get your first taste of beheading".

The prosecutor also told the court how despite being placed in a government de-radicalisation programme, the teen had threatened teachers in the past, telling one he would "cut his throat and watch him bleed to death". He also openly stated his desire to become a jihadist and spoke of his admiration for Osama Bin Laden and the Charlie Hebdo attackers.

Mr Greaney told the court that in an online exchange on 19 March, the defendant encouraged the Australian teen to attack police using a gun, a car or a knife. He told the court: "Mr Besim expressed a preference for a combination of a car and knife attack and [the defendant] advised him to buy a machete and sharpen it, run over a police officer and then decapitate him."

"He also spoke of his desire to be a suicide bomber, stating that if he had to choose where to detonate his bomb it would be on a plane in order that he could maximise the fatalities," Mr Greaney added. The two also discussed producing a martyrdom video to be used as propaganda.

James Pickup, QC, defending, told the court that although he accepted the "seriousness of the offence he committed over a period of nine days in March of this year", the boy has made considerable progress and should not now considered "dangerous" for the purposes of sentencing.

The hearing is expected to conclude on Friday (2 October). Anzac Day, held annually on 25 April, commemorates Australian and New Zealand soldiers killed during World War One and, more broadly, all wars, conflicts and peacekeeping missions.