I'm swimming the Great North Swim (a 1 mile circuit of Windermere Lake) on 8 June to raise money for the phenomenal work of Teenage Cancer Trust, a charity very close to me both personally and professionally. I'm raising money to help support young people like my best friend Matt. My friendship with Matt is the reason I now work for Teenage Cancer Trust, and have the privilege of seeing their incredible impact every day.

Matt and I were friends for over a decade, we lived together, annoyed each other, supported and uplifted each other through the best and worst times of our teens. We both moved to London at similar times, in our early twenties, chasing the same dreams of wanting to 'do good' in the public sector, and lived just half a mile away from each other in Haringey.

On a night in 2015, aged 26, Matt turned up on my doorstep, with some news from a physio that the 'niggling knee pain' he'd been feeling might be something more serious. We did what we always did when we needed to think - headed straight to the pub, drank beer and joked that at least he had a great hat collection to cover any baldness, in case that niggling knee pain might be something beginning with C. He left to travel back north, where we're from, and head straight to hospital, on radiographer's urgent advice, and it's not an exaggeration to say things were never the same again.

Matt never made it back to London. He underwent emergency surgery to amputate his entire left leg, and his diagnosis of Osteosarcoma was not only rare at his age, but aggressive, dangerous and continued to take him with a vengeance. He quickly developed secondary cancer, had a huge operation to open his chest and remove secondary tumours in his lungs, went through chemotherapy, radiotherapy and finally secondary sarcoma in his sternum and pelvis.

During this, our friendship grew even stronger. We navigated him feeling like an 'old person', he talked, I listened, and we tackled stupid sports events together. I took up swimming outdoors so I could swim a mile in the Serpentine whilst he simultaneously swam the same distance in his local pool, slogging length after length (with one leg!) when he was unable to make the journey to London to join me. He packed up his crutches and prosthetics and completed the Great North Run (famously being the last person across the line and making it onto the local news!), and continued his passion for MMA and swimming until he no longer could.

Matt died aged 28 - surrounded by his incredible family and grumpy cat, and I was privileged to be his best mate until the very end. I was given the honour of being a pallbearer at his funeral, and vowed to keep swimming, and keep trying to do good things for good organisations.

There are hundreds of Matts out there, each one with their own story, and Teenage Cancer Trust provides an incredible service to teenagers and young people just like him. The importance of age-appropriate care cannot be underestimated, and I'm so proud to be able to fundraise for such a vital charity when financial times are so difficult for so many people.

I can't wait to swim the Great North Swim for Teenage Cancer Trust, and for Matt, and any amount (no matter how small!) will have a genuined impact on this brilliant charity.