A mock-up of two carriages of the new fleet of trains which will run on the Thameslink rail network through Blackfriars, London Bridge and Elephant & Castle has been unveiled.
The full-size mock-up is open to the public this Wednesday at the ExCel centre in east London.
Platforms at many stations have been extended to allow 12-car trains to serve more destinations.
The German-built Siemens class 700 trains will be introduced into passenger service between 2016 and 2018, replacing the class 319 trains which date from 1988.
In 2018, when the new London Bridge Station is completed, there will be up to 24 trains an hour at peak times through Blackfriars to St Pancras International.
"We are transforming our railways through the biggest programme of rail investment ever," said rail minister Stephen Hammond.
"These exciting new trains, combined with the wider Thameslink Programme are a real boost to UK Plc, creating thousands of jobs in construction and across the supply chain, which is driving forward our economy.
"Once operational they will provide a huge benefit to the hundreds of thousands of passengers who travel into London every day. It will vastly improve train travel providing fast, reliable and more frequent services."
First Capital Connect operates the current Thameslink franchise and has worked closely with the government to develop the new trains. MD David Statham said: "This new fleet will give passengers more trains, more carriages and more capacity which our passengers desperately need.
"The Thameslink Programme will deliver more than double the number of carriages across the heart of London. At London Bridge alone the programme will deliver 60 per cent more carriages in the morning rush hour.
"There'll also be exciting new journey opportunities from places along the route from Cambridge and Peterborough across the Thames to Blackfriars and beyond."
The mock-up is open to the public on Wednesday 29 January from 2pm to 8pm at ExCel in the Royal Docks.
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