A former altar boy has been jailed for 15 years for planting a home-made bomb on a busy Tube train.

Weapons-obsessed Damon Smith built the device at home with a £2 clock from Tesco after finding an online al Qaida article entitled Make A Bomb In The Kitchen Of Your Mom.

Smith, 20, claimed it was a Halloween prank, but was found guilty of possession of an explosive substance with intent following a trial at the Old Bailey.

The defendant smiled in the dock as Judge Richard Marks QC sentenced him to 15 years in a young offenders' institution with an extended period of five years on licence.

The judge said that although Smith had an interest in Islam, he was not motivated by terrorism.

But he told the defendant: "Quite what your motives were and what your true thinking was in acting as you did is difficult to discern with any degree of clarity or certainty.

"Whatever the position, the seriousness of what you did cannot be overstated, not least against the background of the fear in which we all live from the use of bombs here and around the world, an all too timely reminder of which were the events in Manchester earlier this week."