Sean Piner, 48, was sentenced to death along with Britain’s Aiden Aslin this week in what the British government called a “fake” sentence. The couple was arrested in April while fighting as part of the Ukrainian army to defend the southern port city of Mariupol against Russian invading troops. Following their trial by the self-proclaimed Donetsk People’s Republic, a Russian puppet regime backed by Vladimir Putin, the Piner family described the situation as “awful.” A statement from the Foreign Ministry said, “First of all, our whole family is devastated and saddened by the outcome of the illegal demonstration trial by the so-called Donetsk People’s Republic. “As a resident of Ukraine for more than four years and serving as a Marine on the 36th Brigade, of which he is very proud, Shaun should have all the rights of a prisoner of war under the Geneva Conventions and including full independent legal representation. . “We sincerely hope that all parties will work together urgently to secure Shaun’s safe release or exchange. “Our family, including his son and his Ukrainian wife, loves him and misses him so much and our hearts go out to all the families involved in this awful situation.” Both families say Piner and Aslin, 28, were fighting legally as part of the Ukrainian army and should be treated as prisoners of war. Boris Johnson called on his ministers to do “everything in their power” to secure the release of the men, who were convicted along with a Moroccan national. Subscribe to the First Edition, our free daily newsletter – every morning at 7 p.m. BST A spokesman for No. 10 said: “The Prime Minister was shocked by the condemnation of these men. “He was closely following the case and asked the ministers to do everything in their power to try to reunite them with their families as soon as possible. “We fully condemn the false death sentence of these men. “There is absolutely no excuse for this violation of the protection to which they are entitled.” Ukraine’s ambassador to the United Kingdom, Vadym Prystaiko, has suggested that talks on a possible exchange of prisoners with Moscow were already under way. He told BBC News: “It will be an exchange. “The important question is what the price will be for this, because the Russians have been talking about exchanging some Ukrainian MPs for them, especially for those who, I understand now, have been working for them all these years.” Meanwhile, the foreign minister said she had spoken with her Ukrainian counterpart, Dmitry Kuleba, “to discuss efforts to secure the release of prisoners of war held by Russian proxies.” Liz Truss wrote on Twitter: “The decision against them is a clear violation of the Geneva Convention. “The United Kingdom continues to support Ukraine against Putin’s barbaric invasion.” The United Kingdom’s Secretary of Defense Ben Wallace paid an unannounced visit to Kyiv for talks with Ukrainian President Volodymyr Zelensky on Friday.