Due to the age of most of the UK's railway network, most elevated railways were constructed using brick and not in steel-above-street style. There was once a steel-fabricated elevated railway in Liverpool; the Liverpool Overhead Railway which was opened in 1893, but that closed in 1956.
Due to the historic nature of brick elevated railways, they didn’t lend themselves to running above roads. Instead the arches beneath were converted into commercial and industrial uses (offices, breweries, restaurants, bakeries, clubs, and a whole host of other uses) which are in high demand; I’ll have to do a photo tour, because you can stumble upon interesting and unique environments.
Focusing on London, there are numerous elevated sections throughout the city due to the hilly topography, with most found on the commuter routes into Central London. The approaches into London Bridge, London Fenchurch Street and London Waterloo are the most notable examples, constructed from untold millions of bricks. The most impressive elevated railway is the London & Greenwich Railway, which now forms the backbone of the South Eastern Main Line and Chatham Main Line. Opened back in 1836, it is the oldest elevated railway and oldest commuter line. It is impressive not just for its age, but its sheer size, the number of tracks and length. It is probably to this day one of the largest elevated lines on the planet. The section above Borough Market is particularly interesting as it weaves between buildings.
South Eastern Main Line/Chatham Main Line
Image taken by Alex-397 on Flickr: https://www.flickr.com/photos/lought...576267/sizes/l
Image taken by parkgateparker on Flickr: https://www.flickr.com/photos/442082...197146/sizes/l
Image taken by electricfoto on Flickr: https://www.flickr.com/photos/tewalk...521241/sizes/l
Bonus video:
• Video Link
South West Main Line
Image taken by Jon Bowers on Flickr: https://www.flickr.com/photos/288501...714538/sizes/l
London, Tilbury & Southend Line
Image taken by Doolallyally on Flickr: https://www.flickr.com/photos/levett...136699/sizes/l
Thameslink
Image taken by mattbuck4950 on Flickr: https://www.flickr.com/photos/mattbu...190627/sizes/l
Great Eastern Main Line
Image taken by Always Santa Fe on Flickr: https://www.flickr.com/photos/tunnel...934962/sizes/l
West Anglia Main Line
Image taken by London Less Travelled on Flickr: https://www.flickr.com/photos/london...869587/sizes/l
Image taken by terencechisholm on Flickr: https://www.flickr.com/photos/224865...215864/sizes/l