A Cheshire businessman has admitted to buying cannabis and turning it into what he claims was a painkilling oil to help his terminally ill brother, in an attempt to highlight “the stupidity and cruelty” of drug prohibition.

Ben Findlay has told the Guardian he spent up to £5,000 obtaining the drug from criminals earlier this year. He then turned his garage into a makeshift laboratory to convert the cannabis into a medicinal mix that his brother Eric, who had cancer, ingested in the weeks before his death.

Findlay, a 36-year-old entrepreneur, said he was willing to face prosecution over buying and “cooking” the cannabis as an alternative to morphine.

Speaking at his home on the Cheshire/North Wales border, he said his brother Eric, who was 14 months older than him, was a supremely fit, highly driven character. “He was diagnosed with cancer which had spread in April, shortly after Easter, which was a terrible shock to us all given that he had a very healthy lifestyle.

“People used to call us Danny DeVito and Arnold Schwarzenegger from the film Twins. Given how fit Eric was, I was obviously Danny DeVito,” he said.

Ben Findlay said his brother decided after being told he was terminally ill that he wanted to be lucid throughout his end of life care.

“Very quickly after diagnosis, Eric was in a lot of pain as the tumours spread and the medical team offered him codeine, and eventually morphine. At first, we thought there was some hope through alternative immunology therapy that might have saved him. So that meant he had to stay off morphine because he would have been too weak from it to go on that programme.

“Eventually, when it was clear he was going to die, Eric told us he wanted to be calm, clear, lucid and in charge of his affairs. I had been looking into medical cannabis as a possible alternative to the morphine because he feared that that would knock him out most of the time. I was determined to meet his wishes. I managed to contact a pharmacist who guided me as to how to convert the cannabis into a liquid form that Eric could ingest. All the time, Eric stressed that this was what he wanted; this was how he wanted to be treated for the pain.”

Ben Findlay (right) with his brother Eric. Photograph: Christopher Thomond/The Guardian

Transforming his garage into a makeshift lab, Ben Findlay said he was able to process the cannabis into a sludge.

“I put the sludge into those syringes that you give kids medicine like Calpol with and Eric was able to squeeze them out and swallow them when the pain really kicked in. Right up until the last day of his life I said that it was an effective pain relief. Most importantly he stayed lucid to the end and was able to make decisions about his family’s future, and crucially say goodbye properly to his wife Mo and his two children. He told his wife that he loved her very much and that his children were beautiful.

“He might have been high and calm with the medical cannabis I made up for him but Eric was there with us, he knew what he was saying, he was able to say those very important things at the end,” Ben Findlay said.

Asked about his admission over buying and processing the cannabis, he added: “I know I was risking my liberty, my business, my family but I have no regrets giving Eric a relatively pain-free, lucid last few weeks with those that loved him all around.

“If I was arrested now I would not accept a caution; I would prefer to be tried by my peers in court. The law becomes redundant when it stops protecting people. Prohibition did not protect my brother. Eric wanted medicinal cannabis for his final few weeks on earth and it was my duty to get him it. I have absolutely no regrets.”