Nicky Reilly, from King Street, Plymouth, was released from hospital after suffering facial injuries in the blast at the Giraffe restaurant in Exeter.

Upon his release Reilly was placed in police custody.

Devon and Cornwall Police can detain Reilly for up to 28 days under the Terrorism Act at the undisclosed location where he is being held.

The explosive device, made from sodium hydroxide and paraffin, was packed with nails and designed to detonate when it was shaken, sources said.

Reilly emerged from the Giraffe restaurant "covered in blood" when the bomb failed to detonate fully. Two other devices were found nearby.

Police believe extremists took advantage of Reilly's low IQ and history of mental illness to radicalise him.

Reilly had changed his name to Mohammed Rasheed and had a screen saver of the Twin Towers in flames from the 9/11 attacks on his computer, neighbours said.