It's known affectionately as 'the Thumper' - and it passed through Lewisham on Saturday.
The iconic 1950s diesel engine chugged through the station at around 10am with several passengers on board.
It's only the second outing for the Thumper this year, which is privately owned by Hastings Diesels.
Standing at Lewisham.
— Chris Date (@cmpd_date) July 17, 2021
"The next train doesn't stop here"
"Probably a new 707 on test"
1001 goes passed in to Cannon Street! 🤣
*toot* *toot* 🚂@HastingsDiesels @ShunterJack @Peter_Mugridge pic.twitter.com/82vJt7skqr
People were delighted to spot the train at the station.
One said: "Arrived just as it was coming up the hill so was a close one indeed.
"The crossover next to the station is great to watch trains go over too."
It is not clear where the train was going but there is speculation it was a test trip.
The Thumper Returns!@HastingsDiesels 1001 is seen on a Private Wedding charter
— Coastway Will 💜 (@Coastway_Will) July 17, 2021
It'll later form a much less formal charter to Tonbridge! 😂 pic.twitter.com/sDL7Tr3CJy
The next tour will take place on August 7 from Eastbourne to Tonbridge.
This will be the first railtour for 18 months.
In view of the effects of the pandemic, the company has planned a local excursion which avoids passengers being inside the train for very long periods of time.
The day’s outing will start and finish at Eastbourne, and the six-coach train will operate four separate journeys between Eastbourne/Hastings and Tonbridge.
The intention is that customers from further afield can join the train at Tonbridge.
At both Tonbridge and Hastings the train will be withdrawn from service and shunted to sidings for servicing/cleaning.
5Z87 Hastings diesel thumper 1001 passing Stone Crossing (I know nothing about these kind of trains so I hope I am correct 😂) pic.twitter.com/RwPhvrFkPq
— The Station Batsman (@LifeDownTheLine) July 17, 2021
Of the train itself, they say: "Our train is a Diesel-Electric Multiple Unit (DEMU) that worked on the London Charing Cross – Hastings route under British Rail between 1957 and 1986.
"It was subsequently preserved by Hastings Diesels Limited (HDL); we restored it to its former glory and returned it to main-line operation ten years later, in 1996.
"Our train is commonly referred to as Unit 1001, as the first “Hastings” DEMU (all six of whose vehicles we own) was so numbered. Although the train we use on our outings does include at least one vehicle from the original unit 1001, some of its vehicles are from other units - and indeed, other trains."
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