The oldest trains in the Thameslink fleet are being retired today (Sunday 27 August) with the final passenger journey leaving Brighton for Bedford at 6.14pm.
The old trains – class 319s – came into service almost 30 years ago when Thameslink began operating in 1988.
The route used the Snow Hill tunnel – which had been closed to passenger trains for 72 years although it was used for some years by freight trains.
The use of the Snow Hill tunnel enabled north south services to run through London.
The Thameslink route has recently been the subject of a big capital investment programme estimated to cost more than £5 billion.
Along the route London Bridge and Blackfriars stations, among others, have undergone extensive modernisation.
Thameslink has also introduced new rolling stock – a fleet of class 700 trains.
There will still be some older trains – class 377s – on the route but these are less than 10 years old.
One longstanding Thameslink passenger said: “It’s the end of an era.
“Change takes a lot longer on the railways than most people realise.
“The scale of the planning, finance and scheduling is so complicated and long term that it’s easy to underestimate exactly what goes into it.
“Of course it’s vital too and, as most passengers know, the slightest glitch can cause havoc.
“You’ve only got to look at Thameslink or Crossrail or the Channel Tunnel Rail Link to see the scale of it all.
“But passenger numbers have soared in the years since the Thameslink route has been open – it’s actually a real success story.
“And it will be interesting to see whether we might get some progress now on the proposed second Brighton Main Line (BML2).
“It may take years but I think the important decisions will have to be made very soon.”