Det Sgt Nick Bailey, 41, came into contact with killer agent during investigation
He was looking into the Salisbury poisonings of Sergei and Yulia Skripal in 2018
But he too was contaminated after touching the door handle of Sergei's home
He was in hospital for 17 days and quit the force after his poison ordeal
Now he is suing Wiltshire Police's Chief Constable Kier Pritchard