A former Royal Marine says his symptoms of the deadliest type of brain cancer were dismissed by doctors as 'dehydration' and a result of too much screen time. 

James Greenwood, 42, based in Mold, North Wales, began experiencing dizziness and 'constant, dull headaches' in May. 

He visited his GP twice and was told his problems were likely due to a combination of eye strain and not drinking enough water at his desk job at a real estate company.

However, within a month he was experiencing agonising head pain which prompted him to visit A&E and demand further scans. 

Devastatingly, doctors discovered a walnut-sized, grade four glioblastoma — the deadliest kind of brain cancer that grows rapidly — and gave him a prognosis of 12-18 months. 

James underwent brain surgery to remove the tumour on June 28, followed by a six-week course of chemotherapy and radiotherapy.

He is now waiting to see if the treatment has improved his prognosis, before starting a more intensive course of chemotherapy at the end of October.

James has tried to 'savour' each moment since his diagnosis, attributing this mindset to the training he received in the Royal Marines, in which he served for five years from the age of 18.

'For me, it’s about trying to be as normal as possible,' he said. 'There’s a lot of belief in people saying positivity is a big benefit in combating illnesses. I just can’t comprehend in dealing with this in any other way.'

James first noticed something was not quite right with his health on May 24 when he was having a conversation with his brother-in-law and started to feel dizzy.

He said: 'My vision was wobbling a little bit and I needed to have a bit of a sit down. I had always had a clean bill of health so I thought it was a little unusual.'

Soon after, James said he started to suffer with headaches which began as a 'constant' and 'dull' pain.

He booked an appointment with his GP for June 5, when he was told his symptoms were probably linked to dehydration, and he could be overdue an eye test.

James was also given a blood test and an electrocardiogram (ECG), a non-invasive test which measures the electrical activity of the heart, but said both tests came back with 'no concerns'.

After 'plodding along' for a few days, James said he had an unusual episode in Manchester on June 10.

'I was walking across town and it was like an out-of-body experience, everything around me slowed down,' he said.

He secured a same-day appointment with his GP and was told his symptoms were consistent with migraines.

'I’ve never suffered with migraines in the past so I was sceptical. As with the first GP appointment, I was pushing for a scan of some kind – maybe it was a sixth sense or something but I just knew how I felt and I was trying to get some peace of mind more than anything.'

James said he was prescribed migraine relief medication and told to make another appointment by the end of the week if it had not had the desired effect.

Two days later, James said he woke up at about 5am with a severe headache, and went to A&E with his girlfriend.

He was given a CT scan which revealed a three-and-a-half centimetre by three-and-a-half centimetre mass in the right temporal lobe area of his brain.

James’s case was escalated and he was informed by a neurosurgeon that his symptoms were consistent with a high grade tumour.

He underwent brain surgery to remove the mass on June 28 and was told on August 8 that it had been identified as a grade four glioblastoma and he had a prognosis of 12 to 18 months.

'There are some days where you have to kind of pinch yourself and question whether this is actually happening,' James said.

'Receiving the news is incredibly tough and you’ve got that initial period of shock but after that, you’re forced to process it and try and take the good from it.'

 James underwent a six-week course of chemotherapy and radiotherapy with the aim of improving his prognosis.

He completed his last session of radiotherapy on September 19 and will have a rest period for a month before starting more intensive chemotherapy in late October.

He said this, combined with regular MRI scans, should shed a light on how effective the treatment has been.

'Strangely, it’s been kind of liberating,' James said.

'I think everybody’s probably guilty of taking people for granted, your loved ones, friends, family, but it’s had the effect of reconnecting me with certain old friends, I think it’s drawn the family closer.

'It alters your perspective and it’s a bit cliched but you’re trying to savour every moment.'

James said he has tried to adopt a positive mindset, saying his time in the Royal Marines, which he joined in May 2000 for five years, has helped him.

'It instils in you that belief that regardless of what situation or scenario you’re faced with, you can get through it.

'When you’re thrown into that situation, it does resonate and it does make sense.'

On September 21, James and three of his friends ran across the Edale Skyline, a 20-mile hiking route through the Peak District, with the aim of fundraising for Brain Tumour Research, raising more than £14,000 so far.

'It went really well, it was like me revisiting my version of normal, I wanted it to be a complete escape from everything and it served its purpose,' James said. 

'It’s always been one of my bucket list items to raise a fixed amount for charity over the course of my lifetime and the fact we’ve got to the total we have is absolutely incredible.

'In all likelihood it won’t benefit myself, but further down the line for other people who might find themselves in this position, if there’s a bit more investment, development and knowledge around treatment, other people may reap the benefits of that.'