Up to 800 military personnel were involved in 'Operation Morlop' (Picture: MOD).
Salisbury has been declared decontaminated of Novichok after an almost year-long military clean-up following the poisoning of Sergei Skripal.
The former Russian spy's house and 11 other potentially infected sites have now been ruled safe and Wiltshire Council are set to begin the refurbishment of the property after it was handed back to them by the Department for Environment, Food and Rural Affairs (Defra).
A Defra spokesman said: "The completion of clean-up work at Christie Miller Road, Salisbury marks a significant milestone in south Wiltshire's return to normality following the sickening Novichok nerve agent attack last year."
Military teams spent 13,000 hours on the clean-up after Mr Skripal and his daughter Yulia were targeted with the nerve agent in March last year.
Both were left seriously ill but have since recovered.
Armed Forces personnel took 5,000 test samples from across Salisbury and nearby Amesbury, where 44-year-old Dawn Sturgess was fatally poisoned in July.
Ms Sturgess fell ill and died after coming into contact with a perfume bottle believed to have been used in the attack on the Skripals and then discarded.
Her partner Charlie Rowley, 45, was also exposed to the nerve agent but was treated and discharged.
Army Lieutenant General Ty Urch, who oversaw military involvement in the clean-up, said the announcement declared "all of those 12 sites safe".
"Novichok is probably one of the most dangerous and most challenging chemicals in existence today and you don't need very much of it and it's highly spreadable."
An estimated 600-800 specially trained military personnel, including the Joint Chemical, Biological, Radiological and Nuclear Task Force, were involved in the clean-up, named 'Operation Morlop'.
Lt Gen Urch said ambulances used in the initial response also had to be decontaminated during the "slow, deliberate and detailed operation".
Special dressing zones were set up near the Novichok 'hotspots', where teams changed into special respirator suits which included equipment not normally used by the military.
"I think our military personnel have demonstrated genuine courage."
Environment Minister Therese Coffey said the "professionalism" of all those involved in the clean-up had been "exemplary".
Theresa May accused Russia of the Novichok attack in a statement to MPs in September 2018.
Lt Gen Urch said the attack, believed to have been orchestrated by Russia's secret service, was a "despicable act", repeating a comment made by the Prime Minister in the aftermath.
He added the clean-up has been "the longest running" operation of its kind on British soil and that those involved will be "recognised in due course for their courage".