Houthi interrogators broke the arm of a British citizen detained in Yemen when they tried to force him under torture to confess to being a British spy.

Luke Symons, 29, was beaten until he passed out at the jail in the capital Sanaa in the summer of 2018, former inmates told his family. He was arrested the year before in the southern city of Taez when officials manning a checkpoint found he was carrying a British passport, his family says.

Despite the torture, Mr Symons did not confess and a senior Houthi official ordered his release later that year because “there’s no evidence at all against him”, according to a written order seen by The National.

But Mr Symons remains in custody without charge or conviction because of divisions in the Houthi leadership. He is also seen as a useful bargaining chip to secure the release of captured Houthi fighters, British officials said.

“It doesn’t suit their purposes to let him go ... they don’t listen. They are not subject to pressure,” former British ambassador Michael Aron told the family last year.

The torture suffered by Mr Symons follows a pattern of brutality in jails in the Yemen with former detainees telling Human Rights Watch that guards beat them with iron rods, shackled them to the walls and threatened to rape them or their family members.

The group said in a 2018 report that it had documented dozens of cases of “arbitrary and abusive” detention by the Houthis.

Details of the broken arm were made public in an appeal by rights group Amnesty International for Mr Symons’ release.

His family previously declined to publicly reveal the information for fear of further reprisals by his captors. “He has been beaten for five years,” said his grandfather, Robert Cummings.

He said that he was able to confirm that his grandson had a broken arm during telephone calls made by Mr Symons from jail.

He has been seen just once by an official from the office of the UN Special Envoy for Yemen, the following year, who reported that Mr Symons was in good health.

The family said that he was unable to detail the treatment because he was not allowed a private visit and was accompanied by prison guards during their discussions.

Mr Symons, from Cardiff, Wales, is being held in solitary confinement but has been able to telephone his family from the jail. He told his family that conditions at the jail were having a serious impact on his physical and mental health.

His MP, Kevin Brennan, said that Mr Symons was an innocent victim of the conflict and has repeatedly urged the UK government to do more to secure his release.

Mr Symons, who converted to Islam as a teenager, travelled to Yemen in 2012 to deepen his knowledge of the Muslim faith before the outbreak of major fighting in the country. He married a local woman and they have a young child.

After the start of the war, Mr Symons sought help from the UK authorities in Addis Ababa in Ethiopia. But British officials would not issue his wife with a travel visa and he returned to Yemen. He was subsequently arrested.

“As he approaches his 30th birthday I call for his captors to release him on humanitarian grounds so that he can be with his wife and child,” Mr Brennan said.

“I also call for the UK government to begin a new initiative to help secure his release before his mental and physical health deteriorate any further.”

Amnesty has called on the Houthi authorities to release him unless he is charged with a crime and called on British officials to step up their efforts to help him.

Sacha Deshmukh, Amnesty International UK’s chief executive, said: “Luke has already endured almost five gruelling years behind bars and it’s long overdue that the government properly engage with his family and exert sustained pressure on the Houthis to get him out of jail and back home to Cardiff.”

The British Foreign Office said it was consistently raising the case with senior figures within the Houthi regime.

“We know this is a difficult time for Luke Symons and his family," a spokesperson said. "Our staff have been working intensively to secure Luke’s release.

"We remain in close touch with his family who we have been supporting since 2017."