The Architecture the Railways Built - Season 4

Tim heads north of the border to scale a Scottish railway icon - the Forth Bridge, without doubt one of the engineering wonders of the world. Tim conquers his fear of heights to learn its story from its foundations, deep under the Firth of Forth, to its summit 110 metres above the water. At Goathland, North Yorkshire, is a railway station where movie magic was made, possibly better known today as Hogsmeade from its starring role in the Harry Potter films.

In Manchester's Castlefield area, Tim discovers how viaducts still dominate the cityscape. In Reading, a railway station is transformed and ready for the commuter challenges of the 21st century.

Tim goes deep beneath the waves to explore the Channel Tunnel, stopping off at Ashford International to take in this underappreciated piece of 90s railway architecture. Folkestone Harbour Station, once a great hub for international travel, is leading the way for the regeneration of a whole area of the town.

Tim gets to grips with his local station - London Bridge, meeting the architects who turned this one-time Frankenstein's monster of a station into the bright, airy and tranquil modern terminus. At the National Railway Museum, Tim gets access to Borough Market Junction Signal Box.

Tim visits the striking post-war Coventry station.? In Scarborough he discovers the birthplace of Britain's funicular railways.? And in a TV first, Tim delves into Network Rail's archives.

Tim explores railway ingenuity at Goole swing bridge in Yorkshire and takes in Edinburgh Waverley from roof to underground vaults.? At the National Railway Museum learns how railways demarked their land.

Tim Dunn sees how quirky railway architecture has shaped the city of Lincoln.?The rivalry of two competing Victorian railway companies and their refusal to share infrastructure not only resulted in two railway stations, but two level-crossings that cut the busiest thoroughfare in the city in two.

In Birmingham, Tim takes an exclusive look at a brutalist signal box, just before it switches off the lights, for the very last time. And, at the Network Rail archives Tim gets his hands on Stephenson's drawings for two great Victorian bridges - the Newcastle High Level Bridge and the Britannia Bridge.

Tim revisits his childhood holiday haunts in South Devon, following the route of Brunel's experimental atmospheric railway.? In Wingfield, Derbyshire, Tim checks in on an ambitious restoration of an early rural railway station.? And, at the National Railway Museum in York Tim finds out how Great Western Railways embraced the holiday business in the 1930s by exploring their railway posters from the era.

Tim explores the birthplace of British locomotive manufacturing - Leeds. Starting at the Round Foundry, the combined engineering works that turned out Salamanca, the world's first commercially successful steam locomotive. In Halifax, Tim discovers a story from the beginnings of the railways, when the canal was still king, and railway architecture demonstrates the rails' deferential position.

And at the National Railway Museum in York, Tim dishes up the facts on railway dining, including the unusual story of Swindon Refreshment Rooms.

Tim explores the surprisingly beautiful Hull Paragon station, a spectacular example of how George Hudson, "the Railway King" indelibly left his mark on the city. But not all the rail passengers who passed through Hull were able to experience the grandeur of this station, as Tim reveals in the much less known railway story of the 2.5 million migrants who passed through Hull station, on their way to a new life in the new world.

In Leamington Spa is a strikingly rare art deco station, funded by a loan scheme designed to create jobs during the Great Depression. And, at the Network Rail archives, Tim discovers some railway war memorials and understands the impact of the Great War on railway workers throughout the UK.