The clip, from a three-day live BBC programme Trainspotting Live, showed engineer Dick Strawbridge breathless with excitement as the freight train rumbled through Doncaster station last night with the "unbelievable" moment being broadcast live to the nation.
Perched at the end of a platform, he told the BBC4 show's presenter Peter Snow: "Unbelievable! We've had an amazing evening, topped off by 66779 Evening Star was here!"
The clip shows Dick and another rail enthusiast watching as the GBRf freight train slowly trundles through the station.
"It's here!," he announces to the camera. "That is unbelievable! We were told it would be two hours late. How pleased are you to see that?"
"Brilliant," it really looks nice doesn't it?," replies his colleague as the evening sun glints off the train's freight trucks.
Jim Waterson, political editor at UK news website Buzzfeed shared the clip on Twitter, writing: "This clip of two men in Doncaster losing it over a train was broadcast live on BBC last night. Amazing. Pure joy."
The tweet has been shared more than 200 times and seen by hundreds of people after going viral.
The three night live broadcast on trainspotters got under way last night with live segments from Doncaster station.
Trainspotting Live promises "nights of spotting, joy and excitement" on BBC Four as Snow, mathematician Dr Hannah Fry and engineer Dick along with a team of rail train enthusiasts revel in the tantalising intricacies, trade secrets and true pleasures of trainspotting... live!
The show's audience is being asked to join the spotting by recording the most frequent to the most elusive trains on the tracks all over country during the three days of live broadcast.
A BBC spokesman said: "This is not just a show for the thousands of trainspotters out there; this is a show for anyone with a passion for British history, travel and engineering. This is a love letter to trains told by trainspotters – the custodians of our train history."
The show will be screened live on BBC Four tonight and tomorrow from 8pm to 9pm