We’ve just reached the top of Shap summit, the highest point of our ride today. It’s been a long, steady climb, chasing the last of the day’s light. In our group of five cyclists, there have been seven punctures already today. We are far, far behind the rest of the 70+ riders going from Preston to Penrith, dodging what have been occasionally heavy rain showers. We already have 70 miles under our wheels and there are still 20 miles to go. It’s just got dark and three of our headlights have died. We’re about to descend the highest climb of the day on roads that might be strewn with invisible potholes and scattered with yet more puncture-inducing thorns. Why are we doing this again?

Two hours later we are welcomed into a small community hall in Penrith, where it's warm and dry and there's an urn in the corner. We drink tea and eat crisps, smiling, joking, laughing, hugging. Despite it being dark and cold, despite the many puncture delays, this has been my favourite ride of the journey so far. The views were epic, the miles long but rewarding, the teamwork and camaraderie that got us safely off that pass in the dark electric. This is why I love riding my bike.

Lots of people have asked me why I’m cycling from London to Glasgow, a 500+ mile ride through unpredictable weather and demanding terrain. It will take eight days when I could make the journey in four hours by train.

There are many reasons why.

To start with, I’m a long-distance cyclist. Ever since my first bike tour, 4,000-miles around the coast of Britain, I have been addicted to exploring by bike. Discovering the UK from the saddle never gets tired. It’s always an adventure to re-visit the familiar parts and discover new places. It’s rewarding and challenging and creates experiences and memories you are never likely to forget. This is meaningful, purposeful travel.

Secondly, Glasgow is where the COP climate summit is being held. As a climate activist, I want to be there, to be counted and to add my voice. I want to put pressure on our politicians to enact policies that will keep our human activities within planetary boundaries. Judging by the outcomes of past COPs, I'm not hopeful, but I see it as part of the movement for change. I know my one voice won’t influence much. But if I don’t speak, I definitely won't be heard.

I’m also riding in a professional capacity, as the director of the campaign group Flight Free UK. Our mission is to raise awareness of the climate impact of aviation and inspire people to travel by other means, so it makes sense for me to travel to the COP in the lowest-carbon way possible. For months we have been asking people not to fly to the climate conference, especially if they live in the UK or Europe, but instead, travel by rail or coach. While most people wouldn't choose to cycle from London to Glasgow, showing that it’s possible might make the coach or train seem just that little bit more achievable.

There are two and a half more days of riding to get to Glasgow, and if these past five days are anything to go by they will be challenging, epic and wonderful. We will roll into Glasgow feeling a special bond to those we’ve met and made friends with along the way, with slightly sore legs and slightly toughened bums.

There are so many things that can and should happen as a result of this conference, and I’ll be standing on the streets with thousands of others over the coming days, demanding better climate action from our leaders. When it comes to transport and aviation, the government is relying on green technology, ‘sustainable’ fuels and offsetting to bring down emissions, even though these measures are not reliable or fast enough to make a difference in the time we have available. What we actually need to be doing is reducing demand: getting out of the sky and staying firmly on the ground.

The bicycle is a good place to start.