It is one of Britain's most secretive sites, remaining shrouded in mystery for more than 100 years.
But this week Porton Down found itself at the centre of one of the biggest diplomatic crises the UK has faced in recent years.
The top secret defence base in Wiltshire was instrumental in helping identify the nerve agent used to poison a former Russian spy in Salisbury.
Read more at:
https://www.mirror.co.uk/news/uk-news/inside-porton-down-britains-controversial-12192830
