A SUSSEX man has admitted sending a hoax "anthrax" letter to the Prime Minister.

Vincent Potter, 60, claimed the potentially lethal powder was contained within correspondence posted to Theresa May.

But the threat never reached its intended target after specialist postal workers intercepted the malicious mail.

No anthrax was found within the letter but Potter was arrested in a counter-terror probe, although he was never charged with a terror offence.

He appeared at the Old Bailey on Friday charged with making a noxious substance hoax on or before August 23 last year, under section 114(2) of the Anti-Terrorism, Crime and Security Act 2001.

Potter, from the village of Mayfield, in East Sussex, sat in the dock wearing glasses, a checked shirt and a blue and white striped tie.

He reached out his left hand to steady himself as he spoke to confirm his name before pleading guilty to a single charge.

"I have been authorised by my barrister to plead guilty," he said.

The charge states Potter "communicated information, namely that a letter containing anthrax, knowing or believing the information to be false, with the intention of inducing in a person anywhere in the world a belief that a noxious substance or other noxious thing was likely to be present in the letter and thereby endanger human life or create a serious risk to human health".

Judge Anthony Leonard QC adjourned sentencing until November 2 for probation and GP's reports to be prepared.

Potter was released on conditional bail.

"The fact you have pleaded guilty will be taken into consideration by the sentencing judge in your favour," he told Potter.

"You must understand this is a very serious offence and the sentencing options are very limited."

Prosecution documents drawn up at the start of the case state: "It is alleged that Potter sent a letter that said that anthrax was contained within it, addressed to the Prime Minister.

"Specialist postal workers intercepted it. Anthrax was not, in fact, found within the letter."