According to Russian state media, two more Britons were captured in Ukraine by Russian forces and charged with being mercenaries.
Dylan Healy was a volunteer chef and aid worker who was captured at a checkpoint on April 1.
Russia released the video of Andrew Hill wearing a military uniform on the same day to announce that he had surrendered.
This comes just a month after Shaun Pinner, a British man, and Aiden Aslin were sentenced to death.
In the hearing held at the Russian proxy court in eastern Ukraine they were charged with the same offenses as Mr Healy or Mr Hill. This court is not internationally recognized.
Since then, the European Court of Human Rights intervened to demand that the sentence be vacated.
Russia rejected the request, stating that it does not implement the Strasbourg court's decisions anymore and that the fate of these men was up to the pro-Russian breakaway Donetsk People's Republic.
Russia's Tass news agency reported that an anonymous official of the Donetsk People's Republic said Mr Healy would be tried for "mercenary activity". According to the report, both men refused to cooperate with investigators.
The charges have not been confirmed by an independent source.
According to the Foreign Office, it condemns the use of civilians and prisoners of war for political ends.
A spokesman said that they are in constant contact and support the efforts of Ukraine to release them.
The Presidium Network, an aid organization working in the region, reported that Mr Healy was captured earlier this year. It stated that he and Paul Urey had been independently carrying out humanitarian work near Zaporizhzhia.
According to reports, Mr Healy was driving with Mr Urey at the time of their capture to rescue a family from a south-facing village.
It is not clear where Mr. Urey is at the moment. Linda Urey, his mother, asked his captors to allow him to return home to her and his children in April.
Healy, who is a chef by training was originally from Huntingdon, Cambridgeshire.
Dominik Byrne was co-founder and president of the Presidium Network. He said that his organization had evidence that Mr Healy was an independent humanitarian volunteer who was not involved with any military action.
His group was in constant contact with the Healys, who were "very afraid" and wanted their son back as soon as possible, he stated.
He said that the family had been in touch with the British government as well as the Red Cross, who were trying to access Mr Healy to verify his welfare.
According to Mr Byrne, it was a terrible situation for the men. They were probably being interrogated continuously and kept in horrible conditions.
Russia's defense ministry claims that Mr Hill was taken into custody in the Mykolaiv area of south-west Ukraine. He is believed to have been fighting alongside Ukrainian forces when he was captured.
He was wearing camouflage and he was slinging his arm. Russia released the video. He claimed that he traveled alone to assist Ukraine.
The family of Mr Aslin stated last month that he was told his execution would take place and that time was running out.
Pamela Hall, Pamela's grandmother, said that there are no words to describe the experience.
The UK government, which called the death sentences "sham judgments with absolutely no legitimacy", has stated that Mr Aslins and Mr Pinner should both be treated as prisoners-of-war under the Geneva Conventions.
It stated that it was doing all it could to support them and was in close contact.
Another person, Brahim Saaudun (21-year-old Moroccan man) was also tried and sentenced to the death row.
