Rather than merely living an isolated life in retirement, Mr. Skripal, a former Russian military intelligence officer, continued to provide briefings to spies in the Czech Republic and Estonia, according to European officials.
There is no risk to other guests staying at the hotel at the time, police said.
"It is likely that they were travelling under aliases and that these are not their real names", he said.
A handout picture taken on Fisherton Road in Salisbury, west of London on March 4, 2018, and released by the British Metropolitan Police Service in London on Wednesday, shows Alexander Petrov (right) and Ruslan Boshirov, who are wanted by British police in connection with the nerve agent attack on former Russian spy Sergei Skripal and his daughter Yulia.
The family's lawyer, Litvinenko claimed that he was an agent of the Spanish intelligence Agency and were planning to go to Spain to transfer the evidence of possible links between the Kremlin and Russian organized crime figures.
Polish Foreign Minister Jacek Czaputowicz said at the time that Britain had been targeted in an "unprecedented attack which was the first deliberate use of chemical weapons against a group of civilians in Europe in the history of post-war Europe".
Relations between the United Kingdom and Russia, already frosty, were plunged into crisis over the incident, and Britain persuaded allies around the world to conduct coordinated expulsions of more than 150 Russian diplomats, prompting tit-for-tat retaliation from Moscow.
Less famous than the KGB - or its successor, the FSB - the GRU plays a shadowy but important role in Moscow's strategic plans.
Britain charged two Russians in absentia on Wednesday with the attempted murder of a former Russian spy and his daughter, and said the suspects were military intelligence officers nearly certainly acting on orders from high up in the Russian state.
They said they would not formally demand their extradition, as Russian Federation does not extradite its citizens, but have obtained a European Arrest Warrant for the pair.
British authorities believe the attack was carried out by two men who are said to be members of Russia's GRU military intelligence service.
"I have only seen help from the Russian state", she said.
Police say the suspects, both about 40, flew from Moscow to London on Russian passports two days before the Skripals were poisoned on March 4.
"We have, however, obtained a European arrest warrant (EAW)", said CPS director of legal services, Sue Hemming. They stayed in a hotel in London - where traces of Novichok were also found - and made two trips to Salisbury. They flew out on March 4, hours after the Skripals were found unconscious. We don't yet know where the suspects disposed of the Novichok they used to attack the door, where Dawn and Charlie got the bottle that poisoned them, or if it is the same bottle used in both poisonings. This is with reference to sources in the British government newspaper the Sun.
Ms Sturgess sprayed herself with what she believed to be perfume; she died a week later from Novichok poisoning, but she inadvertently discovered the murder weapon used against the Skripals.
Canada and its allies, however, said they had "full confidence in the British assessment that the two suspects were officers from the Russian military intelligence service ... and that this operation was nearly certainly approved at a senior government level". Police revealed that CCTV showed them in the vicinity of the Skripal house.
Either way, the agents named will never be able to leave Russia again without fearing arrest overseas, since Moscow does not know how much further information Britain may have about their real identities, or their previous contacts with other Russian agents in the West.