Jeremy Corbyn is known for his unusual love of manhole covers, which he notes to be markers of social history. While we tend to think of them as mundane necessities of our drainage system, there is indeed more they can tell us about the history of our infrastructure than first meets the eye.  What are manhole covers and why are they needed? Manhole covers have been around since Roman times, allowing access to inspection chambers so that drainage systems can be maintained. They also serve as temporary storage points for excess water to prevent it from flooding into the streets, and vary in size and thickness depending on location. Specialist manufacturers like EasyMerchant ensure that a range of sizes is available to meet the demands of heavy traffic and densely populated areas, and modern designs prevent unauthorised access to the drainage system.  Street jewellery  Besides their practical use, manhole covers have been described as ‘street jewellery’, often sporting colourful and unusual designs. An example of this is the special edition commemorative manhole cover installed in Whitechapel last year in honour of the engineers who removed the Whitechapel fatberg: a piece of recent history to add to the tapestry of stories told by London’s manhole covers. Commemorative and one-off designs like the one in Whitechapel may appear simply decorative, but over time, they come to tell important stories about a city’s history.  Historic markers  Countrywide, manhole covers have a story to tell; London is just an example, but its sheer size and history makes it a rich source of manhole history. Manufacturers names are embossed on cast iron covers, becoming functional by creating an anti-slip surface. Amongst these names, a glance at a London street might reveal the inventor of the first flushing public toilets, George Jennings. The toilet was so popular that the capital’s sewage system was unable to cope with demand, and this resulted in a large amount of sewage ending up in the Thames, which in turn led to The Great Stink in 1858. Also commemorated on London manhole covers is Thomas Crapper, known for his contributions to toilet improvement, and London County Council Tramways, which picked up an electrical current from slots in the road. The names of telegraph and electrical companies may also be spotted, serving as long-lasting reminders of infrastructures of the past.   Manhole covers are an essential part of a well-maintained drainage system, but they also provide important markers of the history of urban development. With each new cover that we add, we are contributing to the historic stories of our cities.