Ex-British soldier imprisoned by Russia says he feels abandoned in occupied Ukraine

A source close to Davies said the soldier had a serious injury to his leg and "he's getting no help at all". The person added that representatives of the British government had not been in contact with Davies' legal team, who are based in Russia.

Writing to the BBC in March, Davies says he has received only one letter from his sister. The BBC understands he has since received a letter from another relative.

"The attitude towards him in the prison is bad because he's British, [Russia says] he's a mercenary," says Anastasia Shevchenko, a respected political activist based in Lithuania who helps POWs in Russian captivity.

Russian authorities insist prisoners are treated in accordance with law and international standards, and reject accusations of mistreatment.

Shevchenko told the BBC she informed the British authorities of Davies' capture last year after speaking to Ukrainian POWs held in the same prison, who put the two in contact.

She says she informed the British Embassies in Ukraine and Lithuania about Davies' imprisonment: "They thanked me, and that's it…From Kyiv, I got the message that we wish him to be brave, and we think about him, and...that's all."

"For me, this is very strange because [POWs] are starving in prison, they need help immediately," the activist adds, "I sent [Davies] money so he could buy some food there… the food they are given is not enough. Every month they need food, clothes and medication."

The FCDO did not respond to specific requests for comment on Shevchenko's claims.

She says other countries do more than the UK to help their imprisoned nationals.

"[The British] can do everything possible to swap Hayden and give him the support in prison so that he could feel like people around are thinking about him," says the activist, "This is the most important [thing] in captivity, not to be forgotten."

A source in the Ukrainian government with knowledge of the matter told the BBC they're unaware of any "active work" by the UK authorities to assist imprisoned citizens.

Ex-soldier Shaun Pinner, who was captured in eastern Ukraine in 2022, was sentenced to death by a Russia-controlled court and spent five months in Russian captivity with four other British men before they were freed in a prisoner swap.

The UK government was "exceptionally good at keeping in contact with my family", he said, but it played no part in his exchange, which was brokered by the Saudi government.

He believes it's very difficult for the government to get involved in prisoner exchanges: "The best outcome is if it goes through Ukraine. I can understand there's a lot of frustration over lack of access but if Russia doesn't let diplomats in to see POWs, there's not a lot you can do," says Pinner.

The FCDO told the BBC: ""Under international law, Prisoners of War cannot be prosecuted for participating in hostilities. We demand that Russia respect these obligations, including those under the Geneva Conventions, and stop using Prisoners of War for political and propaganda purposes."

In its travel advice for Ukraine, the FCDO advises: "If you travel to Ukraine to fight…your activities may amount to offences under UK legislation. You could be prosecuted on your return to the UK."

It adds that "British nationals fighting in Ukraine have been killed or captured…The British Government's ability to support you in these circumstances is very limited."