The instinct to protect your child is one borne within every parent and arrives with their birth.

Helen Armstrong is forced daily to experience a helplessness no mother would ever wish to endure.

Her son, John, is currently 15 months into a five year prison sentence at Puzhal jail, in India.

He was one of six Britons - and 35 men in total - arrested in October 2013 and accused of illegal weapons possession. They have all strenuously denied the charges, insisting they were simply working for the American anti-piracy firm Advanfort.

She recently returned from a fourth visit to the Chennai jail - and was forced to once again walk away from her son, leaving him in filthy, poor conditions and not knowing when she would see him again.

"Every time it gets harder to leave him there," Helen told the News & Star from her Wigton home. "It's awful, just walking away.

"This time he was standing behind this big gate with iron bars, waving and trying to look cheerful for me."

It was on the back of this visit, that Helen was prompted to write an open letter to the Foreign Secretary, Boris Johnson.

In her heartbreaking open letter, she implores Mr Johnson to help, saying: "In my opinion, the more power a person has, the more ashamed of this situation they should be."

Helen writes: "I feel bitterly disappointed and very let down.

"[John] has resigned himself to the fact that he will have to serve the full five year sentence, despite an appeal pendin. He is only 29 and is missing out on a huge chunk of his young life whoch can never be replaced.

"Surely, at some point soon justice must prevail? But even if it does, justice delayed is justice denied."

Helen, her husband - also called John - and their daughter Joanne Thomlinson have been campaigning tirelessly for John's conviction to be overturned and for him to be released.

A petition with hundreds of thousands of signatures was handed to Downing Street, and there have been numerous meetings with Government officials, charities and even a protest rally.

The 61-year-old said the years without John have taken their toll.

"The last four years have been very difficult. To me it feels more difficult as time goes on.

"It's always with you," she continued. "Happy occasions are still happy, but they are hard as well.

"If we had known then [how long it would drag on] I don't know what we would have done."

The nightmare for the Armstrongs began innocently, when Joanne, 31, sent them a text message.

"My husband and I were on a cruise when it all began," Helen recalled.

"Joanne sent us a message to say John had messaged to say his ship had been impounded in India. We had no idea what that meant - I sent a light-hearted message back, never thinking it could lead to us.

"Then, on the day we were coming home, we got a message to say he'd been arrested."

In the years since John's arrest, family, friends, neighbours and former Nelson Thomlinson classmates and other ex-soldiers have rallied around the Armstrongs and the other Britons.

They have been named the Chennai 6 and include John, Billy Irving, Paul Towers, Nick Dunn, Nick Simpson and Ray Tindall.

Representatives from each of the families - with Joanne acting for the Armstrongs - have been leading the way in demanding meetings with British Government officials, organising petitions and keeping the issue in the public eye.

The public have raised funds to help provide basic food and hygiene products for all of the men, helped cover the cost of lawyers and offered vital emotional support.

Helen said: "We are so grateful to people. It really helps us and helps John; all the support on Facebook and online.

"Every time I go up the street, somebody asks about him. They write letters and send parcels.

"We have people come up and talk to us who have their own big life or family troubles and yet they are so concerned about John.

"It's just amazing, humbling and overwhelming. It has helped us through it."

She continued: "We couldn't have managed without Joanne though: she's been amazing. We are very proud of her."

The men appealed against both their conviction and sentence, with the hearing finally taking place at the end of November.

However, the judge "reserved his decision" with no date for the verdict - and the men are still waiting.

"We're just waiting, for anything," said Helen. "That's why I wrote the letter. We're waiting for news.

"If necessary, if nothing happens shortly, then we want the Government to apply pressure. I would hope our Government can do more."

And, while John may have resigned himself to serving his five year jail term, his mum says that is something she is a long way from accepting.

"John may have resigned himself, but I couldn't do that," she insisted.

"I couldn't get my head around that. I keep hoping it will be over soon."

To find out more about the Chennai 6 or how you can help, visit chennai6.co.uk or search for Forgotten Chennai 6 on Facebook.