A 20-year-old man has appeared in court accused of plotting a terrorist attack after he was allegedly caught with a recipe for mustard gas.

Jordan Richardson, of Oliver Close, Howden, near Goole, East Yorkshire, was at Westminster Magistrates’ Court on Monday accused of engaging in conduct in preparation of an act of terrorism.

He was arrested on December 19 after he allegedly made Instagram posts expressing his support for the terrorist group known as Islamic State.

When arrested, he was found with a document that is said to have set out an attack plan, referring to weapons and killing bystanders, the court was told.

He also had a handwritten recipe for sulphur mustard, a toxic “blister agent”, it is claimed.

Prosecutor David Cawthorne told the court that the recipe had been assessed as viable by experts, and was the kind of gas that could be put in a grenade.

Richardson’s home was searched and police found a crossbow and a knife, the court was told.

Searches of digital devices showed he had expressed a desire to kill or harm infidels and members of the Jewish population, it is alleged.

Research of potential targets included a shopping centre, the court heard.

District Judge Annabel Pilling remanded him in custody to appear at the Old Bailey on January 17.