Aiden Aslin, alongside ex-British Army soldier Shaun Pinner, have been accused of being mercenaries by a Russian proxy court. However, the men say that because they were serving with regular military units in Mariupol, they should be protected as prisoners of war by the Geneva Convention.
This is what you need to know.
Who is Aiden Aslin?
Aslin is a British national and former care worker from Nottinghamshire who has a Ukrainian fiancee and moved to the country in 2018.
He previously fought with Kurdish People’s Defence Units in Syria against the Islamic State group and, according to his family, is part of Ukraine’s 36th Marine Brigade.
Aslin’s grandmother told the BBC that he joined the army because “he made Ukraine his adopted home”.
Why has he been sentenced to death?
Aslin, alongside fellow Brit and former British Army soldier Shaun Pinner, from Bedfordshire, have been condemned to death for fighting Russian forces in a “sham” sentencing.
Both Aslin and Pinner were both already living in Ukraine when Russia invaded, and were captured in April whilst defending the city of Mariupol.
The pair were convicted of taking action towards violent seizure of power at a court in the self-proclaimed Donetsk People’s Republic.
Russian foreign minister Sergei Lavrov defended the convictions as being “guided by the laws of the Donetsk People’s Republic”, the breakaway state controlled by pro-Moscow separatists.
“Because these crimes were committed on the territory of the Donetsk People’s Republic, all the rest is speculation,” he told a press conference.
Interfax, a Russian news agency, claimed the men would be able to appeal against their convictions.
Following the news of their sentencing, the UK Government has insisted the judgement has no legitimacy and that the pair should be treated as prisoners of war.
The Governor of the Luhansk region of Ukraine, Serhiy Haidai, said that Aslin and Pinner would have signed official documentation upon joining the Ukrainian armed forces and that the verdict is therefore “not applicable to them, even if they are not Ukrainians”.
Speaking to BBC Radio 4’s Today Programme through a translator, the Ukrainian politician said: “All the people who come to fight on the Ukrainian side sign documents with the armed forces of Ukraine, hence they acquire official status.
“That’s why they are subject to the Geneva Convention if they’re taken as prisoners of war.
“This kind of verdict is not applicable to them, even if they are not Ukrainians.”
He added: “From what I know the lawyers already appealed against this verdict and I believe what is happening is just political pressure coming from Russia.”
A third man, Moroccan national Saaudun Brahim, was convicted alongside Aslin and Pinner.
What has his family said?
The families of Aslin and Pinner have both called for urgent access to medical and legal help, following the two two being tried as mercenaries by a Russian proxy court.
In a statement to the Newark Advertiser, one of Aslin’s family said: “We love Aiden with all our hearts. He and Shaun, as members of Ukrainian armed forces, should be treated with respect, just like any other prisoners of war.
“They are not, and never were, mercenaries.
“We hope that this sentence will be overturned and beseech the governments of the UK and Ukraine to do everything in their power to have them returned to us safely, and soon.
“We can only imagine what they are going through right now.
“This is a very upsetting development and we ask that our privacy is respected at this time.”
What has No 10 said?
Foreign Secretary Liz Truss said: “I utterly condemn the sentencing of Aiden Aslin and Shaun Pinner held by Russian proxies in eastern Ukraine.
“They are prisoners of war. This is a sham judgement with absolutely no legitimacy.
“My thoughts are with the families. We continue to do everything we can to support them.”
She later tweeted: “Spoke with Ukrainian FM Dmytro Kuleba to discuss efforts to secure the release of prisoners of war held by Russian proxies.
“The judgement against them is an egregious breach of the Geneva convention.
“The UK continues to back Ukraine against Putin’s barbaric invasion.”
A No 10 spokesperson said: “We are obviously deeply concerned by this. We have said continually that prisoners of war shouldn’t be exploited for political purposes.
“Under the Geneva Convention, prisoners of war are entitled to combatant immunity and they should not be prosecuted for participation in hostilities.
“So we will continue to work with the Ukrainian authorities to try to secure the release of any British nationals who were serving in the Ukrainian armed forces and who are being held as prisoners of war.”
Tory former minister Robert Jenrick, who represents the Newark constituency where Aslin lived, called for the Russian ambassador to the UK to be summoned to the Foreign Office.
He said: “This disgusting Soviet-era style show trial is the latest reminder of the depravity of Putin’s regime.
“Russia should be clear, they cannot treat British citizens like this and get away with it.
“Contrary to the Kremlin’s propaganda, Aiden Aslin is not a mercenary. He has been living in Ukraine and serving in its armed forces before Russia’s illegal invasion and as a prisoner of war is entitled to protection under the Geneva Convention.
“The Russian ambassador should be summoned to the Foreign Office to account for this most egregious breach of the Geneva Convention.
“Aiden must be released as soon as practicable.”