The Berlin spy case came as Britain’s relations with Russia could not have been more finely balanced with Vladimir Putin amassing his forces on the border of Ukraine.
After the Cold War ended in 1991, hopes of a warmer co-existence with Russia were gradually snuffed out, culminating in the invasion of Ukraine last year – the largest war in Europe since the Second World War.
Nearly 20 years ago, President Vladimir Putin was welcomed by the late Queen on a state visit to the UK – the first by a Russian leader since 1874 – but raised eyebrows when he kept her waiting for 15 minutes.
Since then, Russia has gone on to cement its rogue state status under Mr Putin, himself a former intelligence officer who first came to power in 2000.
In 2006, there was public outcry at the poisoning of former Russian spy Alexander Litvinenko in a hotel in Mayfair, London.
An inquiry concluded the killing of the outspoken Putin critic, who died after drinking tea laced with radioactive polonium-210, had “probably” been carried out with the approval of the Russian president.
Authorities have faced criticism for failing to appreciate the potential risk to European security when Russia invaded Crimea in 2014 in an apparent precursor to its Ukraine invasion in 2022.
In the wake of the 2016 Brexit vote, there were concerns about Russian interference.
In 2018, members of a Russian military intelligence squad were believed to have smeared a deadly chemical weapon on the door handle of former Russian spy Sergei Skripal in Salisbury, Wiltshire.
Both Mr Skripal and his daughter, Yulia, were left fighting for their lives while a police officer also became seriously ill.
Months later, 44-year-old Dawn Sturgess died and her partner, Charlie Rowley, became seriously ill after they also came into contact with the substance.
Anti-corruption campaigner and prominent Putin critic, Bill Browder, criticised the Government’s response to the outrage on British soil, saying the expulsion of 23 Russian diplomats did not go far enough.
Former prime minister Boris Johnson was later criticised for meeting ex-KGB officer Alexander Lebedev at a social event just weeks after the Salisbury poisoning.
By 2020, then Home Secretary Priti Patel vowed to crack down on foreign interference in the wake of the publication of a long-delayed Intelligence and Security Committee (ISC) report which found ministers had “badly under-estimated the response required to the Russian threat”.
The document suggested there was no proper investigation into whether there had been successful Russian meddling in the EU referendum despite “credible open source commentary” indicating Moscow’s influence in campaigns relating to the Scottish independence referendum two years earlier.
The ISC also warned that successive governments “welcomed the oligarchs and their money with open arms”, and allowed them to forge “connections at the highest levels with access to UK companies and political figures”.
By the time security guard David Smith was leaking secrets to Russian intelligence in Berlin, the British Government was actively “calling out” the hostile state, including for its treatment of opposition leader Alexei Navalny.
Since Russia’s invasion of Ukraine in early 2022, the UK has allied itself firmly with the beleaguered state to oppose Russian aggression through sanctions and support.
Britain is not the only country to be affected by alleged Russian spying activities, with incidents in recent years reported in the United States, Hungary, Austria, Sweden, Bulgaria, Germany and Italy.
Repeated concerns have also been raised over cyberattacks and disinformation campaigns on social media linked to Russia.
