A woman from Surbiton is taking part in this year's Royal Parks Half Marathon in London to raise money for The Brain Tumour Charity.

26-year-old Tilly O'Brien was diagnosed with a benign brain tumour in 2016 at the age of 17.

Studying for her AS-Levels at the time, Tilly started experiencing migraines and noticed during a Psychology lesson in school that she could not wiggle her fingers on her left hand – when she tried to, they would "tremble and shake".

"During the lesson, our teacher was telling us about how the right side of the brain effects the left side of the body and vice versa. She then asked us to wiggle our left fingers and when I couldn't, she told to me to go to my GP," she said.

Following her teacher's orders, Tilly went to her GP for advice, but the GP put her symptoms down to "best case scenario – a little nerve damage, or worse case scenario MS," Tilly said.

Tilly then had several GP appointments which involved different tests until she was eventually referred for a MRI scan, but there was a waiting list of six months.

"Fortunately, someone cancelled their appointment, so I was called in for an MRI in three days, but the words 'brain tumour had still not been mentioned,'" she said.

Tilly added: "I was told I would have to wait 12 weeks for my results, but two days later my mum woke me up saying that we had to go to the hospital immediately – it was a Saturday.

"That's when the fear kicked in. I was diagnosed with a brain tumour seated in the right side of my brain in that appointment."

Tilly was sent for surgery at Alder Hey Children's Hospital in Liverpool, where she was living at the time, for surgery to remove the tumour shortly after her diagnosis.

However, during the surgery, her surgeon found that she had a blood clot on the opposite side of her brain, so he made the decision to end the tumour removal procedure and perform a second surgery on the other side of the brain to remove the blood clot.

"My surgeon said that the surgery to remove the blood clot was as aggressive as being hit by a car and my left side weakness travelled to my leg and face too. I woke up with two sets of stitches on either side of my brain, completely out of it and couldn't do anything myself," she said.

"I was like a baby again. The following weeks consisted of me teaching myself to walk, talk, and get myself dressed again.

"My determination to get better caused me to recover quickly, but I now have long-term disabilities, including left-side weakness and a loss of peripheral vision, meaning I will never be able to drive."

Tilly was a Young Ambassador for The Brain Tumour Charity following her surgery (Image supplied)

Tilly then underwent a third surgery to remove the tumour a couple months later, however, an ECG scanner found that full removal of the tumour could result in full paralysis and blindness, so her surgeon made the decision to leave a bit of the tumour in.

Despite Tilly's treatment taking place at the start of her A-Level year, she still decided to take her exams and went on to study English Literature at the University of Leeds the following year.

Now nearly ten years later, Tilly has yearly MRI scans to check for any growth of the tumour but there has been no sign of growth yet.

Since finishing her treatment, Tilly has been a Young Ambassador for The Brain Tumour Charity (TBC), has spoken at Parliament with the charity, has done a skydive to raise money for it, and has run the Leeds Half Marathon in aid of the charity.

Tilly ran the Leeds Half Marathon in May 2019 (Image supplied)

Now, Tilly is training to run the Royal Parks Half Marathon to raise money for TBC on 12 October.

Speaking about why she chose to take part in the marathon, she said: "The Brain Tumour Charity has been a huge part of my tumour journey – as a young ambassador, I met other tumour survivors like myself, which helped make me feel less alone in my diagnosis and learn more about brain tumours as I was so young and didn't know much about them beforehand.

"I was lucky that a patient cancelled their MRI otherwise I might not be here today. Brain tumour diagnosis times are slow, which can cause serious problems, and the symptoms of brain tumours aren't well known, which can also cause serious problems – that's why The Brain Tumour Charity is so great – because it aims to help speed up diagnosis times and raise awareness of brain tumour symptoms.

"I also chose to raise money for The Brain Tumour Charity because despite being the biggest cancer killer in children and young adults, it has the least research funding of all cancers – the charity is trying to change that, but it needs funding to do so."

Tilly says that her training for the run has been gruelling, especially when she was running during the recent heatwave.

"But as I've already ran a half before, the training isn't as hard this time, and I'm excited for the big day."

Tilly is hoping to raise £2,000 for the charity and has already raised over £1,800.

You can donate to her JustGiving page here.