THE STARTING POINTS
Many of the giant stone castles we know today were actually built around pre-existing settlements known as motte-and-bailey castles. These were the original, rather more modest structures which consisted of a large, protruding mound (the motte) and an enclosed courtyard (the bailey). The motte would either be a natural hill-top - which was the easy choice - or it would be built by painstakingly piling on layer after layer of soil and stone. This was hard, sweaty labour, done using wooden shovels and barrows. One of the largest was at Thetford Castle, which probably took around 24,000 hours of work.
Today, the striking earthworks are all that's left of Thetford Castle, but many other motte-and-bailey castles would slowly grow into majestic icons of the nation. Windsor Castle, for all its lavish grandeur, began as a humble motte-and-bailey castle.
THE MASTER MASONS
To get a castle built, you'd need a master mason. They were among the most respected and sought-after experts of their day, often summoned across vast distances to work on castles and cathedrals. Armed with measuring rods, compasses and other simple tools of the trade, master masons were architects, engineers, builders and overseers all in one.
One such figure was Hugh of Titchmarsh, who worked on Knaresborough Castle for Edward II. It would prove a controversial structure, thanks to its association with Edward's much-despised friend - and rumoured gay lover - Piers Gaveston. Some master masons had a number of soon-to-be-iconic sites on their CVs, with an example being William Wynford, who worked on Windsor Castle, Wells Cathedral, Wardour Castle, and New College, Oxford.
Building a typical medieval castle required blood, sweat and tears, and workers weren't always particularly enthusiastic about the task at hand. When, during his invasion of Wales, Edward I began creating Flint Castle, it was said that craftsmen were brought in from across the country, "guarded by mounted sergeants lest they flee on the way".
It's estimated that well over 2,000 men - from volunteers to "forced" labour - were involved in building the fortress, with at least 300 people being required to chip down trees and around 1,300 diggers put to work creating defensive ditches. Hundreds of carpenters and masons were also put into service. Specialists from abroad were regularly employed on various British castles, whether to refine the plans or provide mountains of bricks.
When you consider the lack of technology, by our standards, it's impressive just how much the medieval workers sought to remake the landscape. Not just in terms of creating ditches, mounds and moats, but in carving up the surroundings to suit the needs of their overlords. A prime example was Rhuddlan Castle in Wales. It was another of Edward I's great structures, overseen by a French master mason called James of Saint George.
One of the challenges was ensuring a steady delivery of building supplies and food to the burgeoning fortress. And that meant creating a three-mile canal from the nearby River Clwyd - an epic endeavour that would have eaten up much of the budget for building the castle. This was overseen by a specialist ditch digger, and took years to complete, but the result was a waterway allowing direct deliveries to the castle by boat.
Creating an impregnable structure was all very well, but the welfare of the inhabitants had to be considered. Top priority would have been securing a source of water, which would come in particularly handy during any violent siege. Wells were duly dug, each one a frighteningly deep abyss to murky depths. During the 1920s, one workman - who had survived being shot in the face in World War One - plunged to his death while trying to clean the well at Goodrich Castle.
The most famous in Britain is one of the wells at Beeston Castle in Cheshire, which is well over 100 metres deep. According to a popular tale, Richard II hid a treasure trove of gold coins somewhere down that well, but such glinting riches haven't been unearthed. Not yet, anyway.