His trial heard that police were called and the Army’s Explosive Ordnance Disposal (EOD) unit – bomb squad – was dispatched to the scene at the Wockhardt vaccine plant on January 27.

Only after the package had been detonated behind a 100m cordon could they be sure it contained no explosive material.

Similar packages sent by Collins to 10 Downing Street, AstraZeneca, a US Air Force base in Gloucestershire, a laboratory in Wuhan and what appeared to be the leader of North Korea, Kim Jong-un, were intercepted.

Collins had developed an “obsessive interest” in the virus and vaccines, his trial was told.

Defence barrister Janice Brennan said Collins has a diagnosed personality disorder and has had an “obsession” with sending letters and packages for around 30 years.

She added: “He is a lonely and bored individual who does find it very difficult to deal with normal life.”

Passing sentence, Judge David Griffith-Jones QC told Collins: “A compulsion to send bizarre communications to different bodies or authorities is one thing and may be considered a harmless idiosyncrasy.

“It doesn’t explain your behaviour here, which was deliberately to send a bomb hoax knowing perfectly well that it would cause fear and mayhem.”

He said Collins’ insistence that the contents of the package were intended to help scientists at the Wockhardt site was “childish and quite perverse”.

Collins was handed a 27-month jail sentence, with the significant time he has already spent on remand to be deducted.

In total of 120 people had to be evacuated and production of the vaccine was halted, though the batch was able to be salvaged later.

The EOD team detonated the device and it was discovered that it contained no explosive material.

Instead it contained a calculator, a garden glove, four batteries, a “yellow biohazard bar”, a service wipe and a quantity of paper, the jury was told.

One of the documents inside contained Collins’ name and address.

When arrested, Collins told police that his intention in sending the package to Wockhardt was to help scientists and the Government deal with Covid-19.

Wockhardt, a global pharmaceutical and biotechnology company, was providing fill-and-finish services for the Oxford/AstraZeneca Covid-19 vaccine – the final stage of putting the vaccine into vials.

Detective Inspector Adam Marshall, Kent Police’s senior investigating officer for the case, said: “Collins was fully aware of the impact his actions would have and chose to impede the vaccine rollout when the programme was still in its infancy.

“Although the device he sent was not a viable explosive, the people at the site had every reason to believe there was a threat to their safety and they acted in a diligent and thoroughly appropriate way.

‘Thankfully the disruption Collins caused was not substantial, but his actions were an unnecessary distraction.”