Britain announced on Tuesday (local time) it would hold a public inquiry into the death of a former Russian spy who accused Russian President Vladimir Putin of ordering his murder, but denied the decision was linked to the Ukraine crisis.
A year ago, the British government declined to order an inquiry into the killing of ex-KGB spy Alexander Litvinenko, who died after drinking tea poisoned with a radioactive isotope in a London hotel in 2006. That led to accusations Britain was appeasing the Kremlin, which has always denied involvement.
Tuesday's announcement comes as Prime Minister David Cameron leads calls for hard-hitting sanctions against Russia, including freezing the assets of Putin's close allies, after the downing of Malaysian airliner MH17 in a pro-Russian rebel-held part of Ukraine last week.
A spokesman for Cameron denied there was a connection between the decision to hold an inquiry and the Ukraine crisis.
"I can very clearly and firmly say there isn't a link," he told reporters.
Litvinenko's wife Marina said she too believed the decision had not been taken as a result of events in Ukraine.
"I am definitely sure it was not taken because of this (the Ukraine situation)," she told reporters. "I was waiting for this since February. I believed one day it would happen."
She told a news conference she did not expect the inquiry would lead to the extradition of her husband's suspected killers from Russia, but would reveal what happened to him.
"I do this not against Russia. I do this for justice, for truth," she said.
The inquiry will be chaired by Robert Owen, the judge in charge of the inquest into Litvinenko's death who has said there is evidence indicating Russian involvement in the murder, Home Secretary Theresa May said in a statement.
Owen himself had called for an inquiry, saying the inquest - a British legal process held in cases of violent or unnatural deaths - could not get to the truth because he could not consider secret evidence held by the British government.
POST-COLD WAR LOW
Relations between the countries fell to a post-Cold War low following the death of the 43-year-old Kremlin critic who had been granted British citizenship. He died days after being poisoned with polonium-210.
British police and prosecutors have said there was enough evidence to charge former KGB agents Andrei Lugovoy and Dmitry Kovtun with murder, but Moscow refused to extradite them, and Lugovoy, who denied involvement, was later elected a lawmaker.
After Cameron took power in 2010, he made a concerted effort to improve relations, with an eye on strengthening trade links.
When May rejected calls for an inquiry last year, she admitted she had taken into account the interests of Anglo-Russian relations, but said it had not been the main factor.
However, it led to accusations from Litvinenko's family that the government was covering up what their lawyers described as "state-sponsored nuclear terrorism" to protect the Kremlin.
Marina Litvinenko launched a legal challenge and, in February, London's High Court quashed May's decision and told her to reconsider the issue.
In his formal submission to the High Court as coroner, Owen wrote that the secret evidence did "establish a prima facie case as to the culpability of the Russian state in the death of Alexander Litvinenko".
Hearings ahead of the inquest also heard that Litvinenko had been working for Britain's Secret Intelligence Service, known as MI6, for a number of years.
The inquiry will start on July 31 and is expected to be completed by the end of 2015, Cameron's spokesman said.