A teenage terrorist who plotted “mass murder” with a nail bomb at an Elton John concert slipped through the net of the Government’s Prevent anti-radicalisation scheme, a court has heard.

Haroon Syed was radicalised after his elder brother was arrested for hatching a separate Islamic State terrorist plot.

The 19-year-old younger brother had his passport seized because of the risk he would join jihadists in Syria, but he was not put on the Prevent scheme.

The Old Bailey heard on Monday that Syed’s turbulent and unstable childhood coupled with his weak understanding of Islam made him vulnerable to jihadist propaganda.

Alyas Karmani, a Home Office expert, said if Syed’s passport had been seized, then anti-radicalisation experts should also have intervened.