A schizophrenic man who sent a hoax "anthrax" letter to the Prime Minister has been jailed.
Vincent Potter began his brief typed correspondence to Theresa May with the words "Dear BITCH" and falsely claimed the potentially lethal powder was inside.
The 60-year-old, who entered the Old Bailey courtroom with a walking stick, said in the letter that it had come from the "Brothers of the Right Hand" and would be a "little surprise" for the whoever who came across it.
The threat never reached its intended target after specialist postal workers intercepted the malicious mail in August last year - and no anthrax was found inside.
Prosecutor Bill Emlyn Jones said that while the person who opened the letter, postmarked August 19, 2017, said they felt a trace of a biscuit-like substance that seemed to disappear, scientific testing had shown no powder present.
Potter, from the village of Mayfield, in East Sussex, last month admitted a charge of making a noxious substance hoax.
His DNA was found on the stamp and a typewriter thought to be the one used to write the letter was discovered at his home, Mr Emlyn Jones said.
The prosecutor added that there was no evidence of any specific terrorist motivation by the letter's author, who wore a shirt, striped tie and cream jacket as he sat in the dock.
Sentencing Potter to 18 months in prison, her honour Judge Rebecca Poulet QC said: "In my judgment the person sending this frightening letter to the Prime Minister intending them to fear for their safety must be punished by immediate custody."
She acknowledged that Potter, who was convicted 13 years ago for making an explosive, which the court heard related to a dispute with a neighbour, has suffered for many years with schizophrenia but said he presents a danger to the public.
She said: "I find this fact (the previous conviction) a very troubling aspect of this case and it is because of that background that I find myself unable to say that you do not present a risk or danger to the public."
The judge said a neighbour and friend of Potter's had said in a letter of support to the court that he had described the offence as a "moment of madness".
Potter, who has 14 previous convictions for 25 offences including criminal damage and burglary, still has "no real recollection of the events", Paula Bignall, mitigating, said.
She told the court her client, who was diagnosed with schizophrenia when he was 19, had not been taking his medication at the time of the incident and described his state of mind as having "degenerated quite significantly" in the months leading up to it.
He had no political affiliation and said he did not know why Mrs May became the target of the letter, Ms Bignall added.
She described him as being "filled with remorse, regret and to some extent a lack of understanding and comprehension as to how he committed the offence".
"He still has no real recollection of the events," she said.
"At the time it seems he may well have been in the grips of delusional episodes."
When questioned, Potter told police he had never heard of anthrax, or the "Brothers of the Right Hand" and said the letter was "nasty, unpleasant and wicked".