It was on my 25th birthday. I was in Rajasthan, in northern India, trying to get somewhere by train, which is never as simple as you think it's going to be in India.
There had been hold-ups, issues with my ticket, a battle to get down the platform unmolested and make my way to the right carriage to take my place and get ready for the journey out west to the desert town of Jaisalmer. Inside the train I was surrounded by the usual crush of Indians and India. I stepped out for a second to grab some air before the train departed.
There's a photo that captures that moment. I'm hanging out of the rusty old blue train carriage, looking bright-eyed and enthusiastic, grinning at this crazy world of wallahs and touts, beggars and chancers, tourists and commuters, amazed and energised by another day in another foreign land, and suddenly coming to a realisation: this is what I want to do.
I want to travel. For the rest of my life, I want to travel.
I'd made some big decisions to get to that place on that day, taken some gambles and made some changes. I'd quit a full-time job a few months before in order to see more of the world. I'd sold up my furniture and bought a one-way ticket heading west, through south-east Asia, through the sub-continent, and then I'd planned to go on to Africa and eventually Europe.
I'd been wondering if it was the right call. No one leaves a perfectly good job in media without another perfectly good job to go to. No one takes a gap year for a third time. But on that day, as I asked a British tourist to take a photo of me on the train, everything seemed like it had fallen into place.
A birthday is the sort of milestone that makes you weigh up your place in the world. Your 25th is a significant one, a quarter of a really good life, a point when you should have started to figure a few things out. And that day I felt like I had.
I was loving the travellers' lifestyle of being constantly on the move, of seeing amazing new things and meeting amazing new people every day. Why not try, I thought, to keep on doing this?
I had the bug. And it would never go away.
I sometimes wonder whether other travellers have a similarly defined moment of knowledge like that, or if it's usually more of a creeping thing. For some people it must be a slow burn, something that just happens over time, when you realise after many years that you've been obsessed with travel all along.
For others, like me, it would be a sudden jolt, a conscious thing. It might be just one experience that triggers it, or one amazing trip that forever changes things. You have the bug.
It can happen at any point in your life. I've got friends who are only just discovering travel in their mid-30s, who are realising that there's a big world out there and it's a lot of fun exploring it. Their money that once went on cars and mortgages is now being funnelled into air tickets and hotels.
Others seem to have been born with the travel bug, or at least would never be able to remember a time when they didn't have it. If your parents took you travelling when you were young then it would just be something you do – always have done, always will.
How do you know you've got the travel bug? For starters, you'll never look at your bank account in terms of how much you've saved, but in terms of how soon you'll be able to travel. You'll think of the next trip not as "if", but "when". You'll give up whatever you have to to make that happen. Travel won't be a luxury – it'll be a necessity.
This bug is both a blessing and a curse. You'll enjoy a life of adventure and excitement. But you'll also feel a perennial need to keep moving. You'll find it hard to settle for everyday mundaneness.
You'll come to value experience over ownership. You'll put enjoyment above success.
And one day you'll see a crowded platform at a train station in the far north-west of India, you'll smell the mix of engine oil and spices and sweat, you'll feel the tug on your sleeve of another tout, another beggar, you'll begin the search for your carriage, your seat, and your place. And you'll love it.