The convoy rolled into the city at dusk on Tuesday to begin the decontamination of nerve agent “hotspots”.
Soldiers unloaded two large metal containers and a military mini-JCB type vehicle in the Maltings shopping area, where Russian former double agent Sergei Skripal and his daughter Yulia were found critically ill seven weeks ago.
The area around the bench where they collapsed is one of nine sites to be cleaned in an operation that is likely to take several months.
The process there will include the collection of samples such as soil, turf and paving stones, then testing, cleaning and retesting to eradicate any trace of the nerve agent novichok.
The operation is being overseen by the Department for Environment, Food and Rural Affairs.
Ian Boyd, the chief scientific adviser of the department, said last week that each of the nine sites could still contain tiny traces of novichok possibly still as toxic as when it was left there.
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The other sites to be decontaminated are two ambulance stations used in the recovery of the Skripals; a police station; Zizzi’s restaurant, where the pair had lunch; the garage where their car was kept; and the home of detective sergeant Nick Bailey, who was also poisoned.
Mr Skripal’s home, where it is thought all three victims were contaminated, and the Mill pub where the Skripals had a drink, are still crime scenes and will be the last to be cleaned.