Police have made a renewed appeal for witnesses to the Salisbury nerve agent attack in an attempt to prosecute Russian military agents over the death of a British mother-of-three.

Dawn Sturgess died when she inadvertently smeared herself with Novichok nerve agent disguised in a perfume bottle and which was discarded by Russian hitmen.

Police launched the appeal a year on from the attempted assassination of Sergei Skripal in Salisbury last March. Colonel Skripal, who had sold Russian intelligence secrets to MI6, survived the attack but Miss Sturgess died.

Her boyfriend Charlie Rowley said he found the discarded perfume bottle on June 27, almost four months after the attack on Col Skripal and his daughter Yulia. Mr Rowley gave the perfume to Miss Sturgess as a gift.

Two Russian military intelligence agents have been charged in their absence with the attempted murder of Col Skripal but cannot yet be linked directly to the death of Miss Sturgess. Counter-terrorism officers suggested yesterday that witnesses may still be deterred from coming forward - raising concern they fear Kremlin reprisals.

Deputy Assistant Commissioner Dean Haydon, Senior National Coordinator for Counter Terrorism Policing, said: “We are determined to bring to justice those responsible for Dawn’s death and Charlie Rowley’s poisoning.