The King's Roads is the name of a vast interconnecting system of roads, bridges, canals and halls established byJohn Uskglass for his own purposes. The King's Roads appear not to obey any rules of normality, inasmuch as they link places not only in England but in other worlds, for example Faerie. Indeed according to Gilbert Norrell "The King's Roads lead everywhere". Norrell also implies that any shadow, or anything capable of offering a reflection - not merely mirrors but even puddles - can act as a gate to the King's Roads, if only a person knows how to open that gate.
In November 1814 Jonathan Strange finds himself on the King's Roads when, challenged to establish his credentials as a magician by Mr Gatcombe and Mr Tantony, he passes through a mirror hung in the Bedford coffee-house. (Lest Mr Strange should be accused of the rashest folly in strolling through a mirror into heaven-knows-what realm, it should be added that a few days earlier he had not only been reading about the King's Roads in Ormskirk but had discussed them with Mr Norrell; so he very well knew they were to be found behind mirrors). On this occasion he eventually emerges through another mirror hung on the wall of a cottage in Hampstead, the home of Maria Bullworth.
On his return Strange is filled with enthusiasm for the roads and moreover feels a greatly-enhanced respect for the magician-king who built them, John Uskglass. He also reports however that the roads have fallen into disuse and, in some places, decay, so that he believes Uskglass no longer needs them. Strange very much wishes to go upon the Roads again and investigate them further, but the anxiety this causes his wife Arabella leads to her extracting his promise not to explore them again without her express permission. Her subsequent 'death' makes the promise perpetually binding on him .
When Strange realises his wife is not truly dead, however, he appears to feel the prohibition no longer has force, as he returns to England and to his confrontation with Mr. Norrell by way of these Roads (or so we are led to believe by the gentleman with the thistle-down hair, who exclaims in great agitation that "I saw him (Strange) last night on the King's Roads, with the Darkness wrapped about him like a mystical cloak!" Moreover when the enchantment holding Arabella in Lost-hope is broken it seems Strange has previously planned a route for her to escape from Faerie which is either itself one of the King's Roads, or something of his own construction that is very similar. Arabella re-enters the world by means of a mirror: she first appears in it fleeing down "an immense corridor" before she reaches the surface, which briefly loses solidity to allow her to pass .
The image here may give us some notion of how the engravings of Messrs. Minervois and Forcalquier, produced to illustrate the sights Strange saw upon the King's Roads, once appeared. (These unlucky works were lost to us along with all editions of this book, suppressed by Mr Norrell.) The two Frenchmen faced a considerable artistic challenge when it came to depicting the King's Roads, since they had never seen them. Still they did their best, and from the description Strange was able to furnish them with arrived at a rendering he evidently felt did some justice to their eerie subject.
Privately he admits to Childermass however that, because of their training, the engravers make their pictures a little too like those of other artists, such as Palladio and Piranesi . The image on this page is from a work by the latter.