In his 96 years Franklin Medhurst has lived through too much, including six years of service in the RAF during the second world war, to stay silent on the EU referendum.

On Wednesday his letter to the Guardian championing the peace and stability he says the European Union has brought the continent went viral. Among the thousands who shared it online was Dan Jarvis, a potential future Labour leader, who said Medhurst knew what was at stake:

The Wales rugby union centre Jamie Roberts, commented:

Medhurst, who lost his hearing from gunfire during more than 2,000 sorties over six years, said he hoped his letter would make people planning to vote leave think twice.

“I was so frustrated at the success of the Brexit camp. I was amazed that so many people were willing to support a leave Europe campaign,” he said. “[The EU] is not perfect, there are many problems, but as long as we’re in Europe we can sort out these problems. Britain has the chance to be a leader.”

Dan Jarvis (@DanJarvisMP) Powerful letter from 96 year-old #veteran Franklin Medhurst. He knows what's at stake next Thursday. https://t.co/OvzNrjv4h4

The letter seemed to strike a chord because of his status as a veteran, giving deeper resonance to his warning about “a return to the early-20th-century chaos of warring states against each other”.

Speaking from his home in Carlton, County Durham, he said: “If I can make a difference, I would be delighted. I have seen what can go wrong in my time, I feel it’s essential to represent those comrades I knew who fell in world war two. They were all fighting for something important. Their lives will be in vain if we leave Europe.”

Many Brexit campaigners have argued that voting to leave the EU is a way to make Britain great again. For Medhurst, who was born in the heyday of the British empire, the UK remains a great but small country that can achieve much more by working with others.

On the hot top of migration, which he agrees should be controlled, he said: “Migration has been around ever since humans have been on this planet. Britain cannot solve that problem on its own. Europe can sort out the problem of managing migration.”

Jamie Roberts (@Jamiehuwroberts) Not usually one for politics but this short piece is spot on. Worth a read #voteIN



https://t.co/5dF20Ya5o8

He compared a leave vote on 23 June to “jumping off the cliff”, and accused Brexit campaigners – a “bunch of jokers” in his eyes – of having no idea of what would happen if the result goes their way.

“The way Brexit says they will be free to govern their own country … if we leave, all we’ll be doing is handing over Britain to the companies and rich people hoping [Brexit] will win,” he said.

Polls have shown that older people are more likely to vote than young people, and more likely to cast their ballot for Brexit. Medhurst, who has five children and 11 grandchildren and great-grandchildren, believes not enough people are taking a long-term view.

“[The Brexit campaign] looks only to tomorrow,” he said. “It doesn’t look to five, 10, 15, 40 years, which is what we have to do. This is my grandchildren and great-grandchildren [we’re talking about]. We have to look half a century ahead for things like climate change. We have to leave an environment that’s best for them.”

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Asked whether he had discussed the referendum with his grandchildren and great-grandchildren, he said: “I don’t talk [to them] about politics and the war but my wife has circulated the letter around the family. They know how I feel.”