Here's the story of how it all happened, told through the original social media posts.
Some Facebook posts from 2016 may no longer be available due to changes in privacy settings or deleted posts. The original X and Instagram embeds are included below.
It's exactly 24 hours now until I start #12in24! Please visit the fundraiser to donate to @SandsUK.
@AdamLeyton Wow! #12in24 sounds so exciting. We are glad to be partners with you on your adventure, Adam. We wish you luck.
At @LondonCityAir for @LuxairAirlines flight to @luxairport ready to start #12in24 tomorrow.
Today #Leeds dad @AdamLeyton is doing his epic #12in24 charity challenge, 12 countries in 24 hours by public transport!
Country 1. 7:01am. Germany. #12in24
View on Instagram
Country 2. 7:44. Luxembourg. #12in24
Country 3. France. 7:48am. #12in24
@AdamLeyton @Leedsteach We can't wait to have you here, Adam. Thanks for including us in your adventure. #12in24
It's been short but sweet, @Schiphol. Thanks for having me. #Country5 #worldrecordattempt
@AdamLeyton It was great having you here. Good luck on the rest of your #worldrecordattempt!
8 out of 12: @AdamLeyton has arrived in Poland on his #12in24 charity challenge.
Waiting for the last bus of #12in24. There's a chance I'm going to do this! #worldrecordattempt
It's nearly time to do this 4km run! #12in24 #worldrecordattempt
@Leedsteach We did it! 23 hours and 52 minutes! #12in24 #worldrecord
New World Record Holder @TopTablePlanner @AdamLeyton well done buddy! 12 countries in 24 hours using public transport. #12in24 #legend
Listen to @AdamLeyton on @BBCLeeds talking about his extraordinary world record #12in24.
Leeds man's record-breaking lightning tour of Europe. #Leeds
Adam's record-breaking holiday itinerary: 12 countries in 24 hours.
British man sets new world record with minutes to spare.
British dad @AdamLeyton breaks world record by visiting 12 countries in Europe in 24 hours.
Brit passes through Luxembourg on 24-hour European dash.
Record battu en passant par le Luxembourg.
Russian-language coverage of the charity record attempt.
Imamo rekord: Obisao 12 zemalja za 24 sata.
Most countries visited in 24 hours: Adam Leyton breaks Guinness World Records.