Fast-forward to 2006, and Kate was planning a gap year whilst in her final year at the University of Sussex in Brighton. She was frustrated by the lack of online information about alternatives to flying, and that lots of "sustainable travel" initiatives were contributing to the fast-growing carbon emissions from aviation.
Kate reached the final of a social innovation competition with the original concept of Loco2 - a one-stop-shop for low carbon travel - and the seeds of the business were sown.
However, the whole reason Loco2 had come into existence was because of Kate's desire to travel. So rather than diving straight into launching a business, she went on an epic round-the-world adventure over two years: by cargo-ship, bus, yacht, a couple of short flights, and of course lots of trains.
In the meantime, Jamie was itching to turn the idea into a reality, but didn't have a clue about how the internet worked. Thankfully he was able to use his passion for cutting carbon to secure a job at a digital agency focused on sustainability, called Torchbox.
Jamie was quick to show off the prototype to Ed Gillespie, a fellow low carbon traveller who Kate had met in Mexico when he was circumnavigating the globe in the opposite direction (read all about Ed's adventures in his book Only Planet).
Ed was so impressed that he became the first non-family member to invest in the business, and by 2010 Jamie had enlisted the help of Eugene Bolshakov in St Petersburg to turn Jon's prototype into something resembling a train booking website.
Then came the tricky part of securing suitable contracts with rail operators to start selling tickets. Realising how important France is to the geography of Europe's rail network, SNCF came first, and by April 2012 Loco2 was officially connected to the French booking system. Next came Deutsche Bahn in Germany, followed by the UK, Spain and then Italy.
Loco2 secured further angel investment from a number of different sources, at one point being featured on the BBC website as part of a story on the "real Dragon's Den".
It could be argued that Loco2 started in the 80s when co-founders Jamie and Kate started an imaginary travel agency in the living room, using brochures given to them by their parents.
The name Kate came up with has a dual meaning, referring both to trains (locomotives) and the notion of "low CO2" travel (there is of course a third meaning of "loco2" - meaning "crazy" in Spanish - and we used to joke in the early days that Loco2 was "putting the mental in environmental").
Kate enlisted the help of her brother Jamie, and used the prize money from the competition to set up Loco2's first website in 2007.
At Torchbox Jamie met a 17 year-old Jon Leighton, where they found a common desire to tackle climate change with technology.
Jon built the first Loco2 prototype in his spare time, while studying computer science at Oxford University.
In 2011 on the strength of Eugene and Jon's work, and with Kate now back from travelling, Loco2 secured its first substantial investment, allowing Jamie and Kate to work full-time on the business for the first time.