Poison pen letter writer who described children as the "Spawn of Satan" and threatened a Dunblane-style massacre yesterday admitted a two-year campaign of sending threatening mail and making malicious calls.

Ian Julian Walker, who earned the chilling nickname Soldier David, was warned at Teesside Crown Court yesterday that he is facing a jail sentence.

The 46-year-old, of Sherwood Road, Thornaby, pleaded guilty to a charge of causing a public nuisance between December 27 1999 and October 22 2001.

Walker handed himself over to police hunting the malicious caller in October last year after detectives issued a public warning about the letter writer who had targeted schools and shops during his campaign.He walked in to Thornaby police station, claiming to be the poison pen letter detectives had been hunting for two years.

He had threatened to murder shop-workers in the Thornaby area for selling fireworks. In one letter, sent to a school, Walker wrote: "For the greater good these children, the devil's work, must be removed from society before it's too late. They have to be destroyed by fire."

Another said: "They are good for absolutely nothing but causing trouble and disturbance, especially to vulnerable people."

As well as children, Soldier David has also singled out staff working for the supermarket group Asda and North-East convenience store chain Bells.

Police said the man has sent around 20 letters and made about the same number of telephone calls.

Walker spoke only to confirm his name and guilty plea in court yesterday.

Stephen Ashurst, for Walker, said his client was on bail under strict conditions including not to contact witnesses and not to enter named Bells and Asda stores in the area.

Judge Peter Armstrong agreed to release Walker on bail while pre-sentence reports were prepared.

He said: "All sentencing options will be open to the court, custodial as well as non custodial."