Costs for various train tickets were estimated to be around $2007.
Before now, a continuous train journey on this route would have ended in Vietnam and only gone on for around 16,898km.
According to Smith, the journey that previously held the title travelled from London to Singapore via Russia's Trans-Siberian Express.
This new journey beats that trip by at least 2000 kilometres. However, one online train aficionado believed it could be made even longer.
Reddit user Shevek99 commented on a thread, writing:"You can make it a bit longer. Instead of starting in Lagos, you can start in Vila Real de Santo Antonio, next to the border with Spain. From there, there is a train to Faro and from there to Lisbon. Is like 20km longer than starting from Lagos".
The impressive length prompted one user on Twitter to draw an amusing parallel between these continent's impressive railway systems compared to the pack of public transport to Wellington airport.
Currently, some stations in the Portugal-Singapore itinerary are not operating due to Covid-19. Whether they will resume next year remains to be seen.
Curious to dip your toes into the world of train travel? We've rounded up 11 once-in-a-lifetime train journeys for 2022.
Closer to home, we discuss what could be one of New Zealand's most beautiful inner-city train journey and take a ride on the country's gorgeous Coastal Pacific train.