A relative of one of the Britons sentenced to death for fighting Russian forces has begged the Government to “do everything in their power to have them returned to us safely, and soon”.

But why are Aiden Aslin and Shaun Pinner being treated as criminals, and what can ministers do to help them?

Why were the Britons fighting in Ukraine?

Mr Aslin and Mr Pinner had been living in Ukraine before the Russian invasion and they were fighting as members of the Ukrainian armed forces.

They were based in the besieged southern port town of Mariupol.

Why have they been sentenced to death? 

The soldiers have been convicted of taking action towards violent seizure of power at a court in the self-proclaimed Donetsk People’s Republic.

The court is not internationally recognised and the eastern Ukrainian republic is pro-Russia.

What has Russia said about their capture?

Russian foreign minister Sergei Lavrov defended the convictions as being “guided by the laws of the Donetsk People’s Republic”.

He told a press conference: “Because these crimes were committed on the territory of the Donetsk People’s Republic, all the rest is speculation.”

Does international law offer the captured Britons protection? 

The UK Government has said the sentences breach the Geneva Conventions – international legal standards for humanitarian treatment in war.

Ukraine’s ambassador to the UK, Vadym Prystaiko, has also said that the death sentence does not exist in Ukraine and so the prisoners cannot be legally given this penalty in the territory.

How could the Government secure their release?There is some hope that President Volodymyr Zelensky could help due to his close friendship with Boris Johnson, and Foreign Secretary Liz Truss has been in discussions with her Ukrainian counterpart, Dmytro Kuleba.

Mr Prystaiko has also said he believes Mr Aslin and Mr Pinner will be swapped for prisoners captured by Ukrainian forces.

He told the BBC on Friday: “It will be a swap.

“The important question is what will be the price for this, because the Russians were talking about some Ukrainian MPs being swapped for them, especially for those who, I now understand, were working for them for all these years.”

Can the Government appeal to Russia?

Former minister Robert Jenrick, who represents the constituency where Mr Aslin lived, called for Russia’s ambassador to the UK to be summoned to the Foreign Office.

But the Government has been resisting calling in the ambassador, saying that they are in conversation with Ukraine instead.

When asked about the Russian ambassador, a spokesperson for Number 10 said: “We’ve raised concerns with Russia before on a range of other issues.

“But to re-emphasise, we want to work closely with the Ukrainian government given these men were members of the Ukrainian armed forces and that’s what provides them with the international humanitarian protections that they are afforded under the Geneva Convention.”