A man has admitted sending a hoax "anthrax" letter to the prime minister.
Vincent Potter, 60, of Mayfield, East Sussex, claimed correspondence posted to Theresa May contained the potentially lethal powder.
The threat never reached its intended target after specialist postal workers intercepted the malicious mail, while no anthrax was found, a court heard.
At the Old Bailey, Potter admitted to making a noxious substance hoax. He will be sentenced on 2 November.
Potter, who was arrested in a counter-terror investigation but not charged with a terrorist offence, told the court: "I have been authorised by my barrister to plead guilty."
Judge Anthony Leonard said: "The fact you have pleaded guilty will be taken into consideration by the sentencing judge in your favour.
"You must understand this is a very serious offence and the sentencing options are very limited."
What is anthrax?
(Source: BBC News)
The anthrax bacterium is one of the most notorious diseases and bioweapons of modern times
It is a potentially lethal infection caused by the bacterium Bacillus anthracis
Microbes form spores that can survive in soil for several years
An animal or human can become infected if they breathe in the spores, eat food tainted by them, or even pick up spores through an open wound
Anthrax kills within days, so infected animals fall ill before they can travel far from the source
Without prompt treatment, death can come quickly