The referral came after he had attended a number of extremist talks in Luton.
However, he refused to participate and mocked their attempts in online conversations with his uncle.
Mr Haydon said: “Prevent officers tried to engage them on a number of occasions because of concerns around radicalisation and extremism.
“Then we saw a pattern of concerning behaviour where they were self radicalising themselves and had made contact with a Daesh fighter out in Syria to seek direction, advice and guidance on how to join Daesh but also in relation to attack planning.
“But the Prevent Programme needs the individual to engage. It needs a willingness on their part, and he refused. He completely refused to engage.”
Following their arrest, in July last year, police had to scour through 66,000 text messages, social media and email messages and seized 64,000 computer files.