When did the Pevensies forget their origins?

Question

At the end of The Lion, the Witch and the Wardrobe we find out that the Pevensies do not remember their English past, nor even how they came to Narnia in the first place:

So they alighted and tied their horses to trees and went on into the thick wood on foot. And as soon as they had entered it Queen Susan said,

“Fair friends, here is a great marvel, for I seem to see a tree of iron.”

“Madam,” said, King Edmund, “if you look well upon it you shall see it is a pillar of iron with a lantern set on the top thereof.”

“By the Lion’s Mane, a strange device,” said King Peter, “to set a lantern here where the trees cluster so thick about it and so high above it that if it were lit it should give light to no man!”

“Sir,” said Queen Lucy. “By likelihood when this post and this lamp were set here there were smaller trees in the place, or fewer, or none. For this is a young wood and the iron post is old.” And they stood looking upon it. Then said King Edmund, “I know not how it is, but this lamp on the post worketh upon me strangely. It runs in my mind that I have seen the like before; as it were in a dream, or in the dream of a dream.”

“Sir,” answered they all, “it is even so with us also.”

“And more,” said Queen Lucy, “for it will not go out of my mind that if we pass this post and lantern either we shall find strange adventures or else some great change of our fortunes.”

“Madam,” said King Edmund, “the like foreboding stirreth in my heart also.”

“And in mine, fair brother,” said King Peter.

“And in mine too,” said Queen Susan. “Wherefore by my counsel we shall lightly return to our horses and follow this White Stag no further.”

“Madam,” said King Peter, “therein I pray thee to have me excused. For never since we four were Kings and Queens in Narnia have we set our hands to any high matter, as battles, quests, feats of arms, acts of justice, and the like, and then given over; but always what we have taken in hand, the same we have achieved.”

“Sister,” said Queen Lucy, “my royal brother speaks rightly. And it seems to me we should be shamed if for any fearing or foreboding we turned back from following so noble a beast as now we have in chase.”

“And so say I,” said King Edmund. “And I have such desire to find the signification of this thing that I would not by my good will turn back for the richest jewel in all Narnia and all the islands.”

“Then in the name of Aslan,” said Queen Susan, “if ye will all have it so, let us go on and take the adventure that shall fall to us.”

So these Kings and Queens entered the thicket, and before they had gone a score of paces they all remembered that the thing they had seen was called a lamppost, and before they had gone twenty more they noticed that they were, making their way not through branches but through coats. And next moment they all came tumbling out of a wardrobe door into the empty room, and They were no longer Kings and Queens in their hunting array but just Peter, Susan, Edmund and Lucy in their old clothes. It was the same day and the same hour of the day on which they had all gone into the wardrobe to hide. Mrs Macready and the visitors were still talking in the passage; but luckily they never came into the empty room and so the children weren’t caught.

However, in Chapter Fifteen of The Horse and His Boy we find that they would regularly talk about their origins:

And Lucy told again (they had all, except Aravis and Cor, heard it many times but they all wanted it again) the tale of the Wardrobe and how she and King Edmund and Queen Susan and Peter the High King had first come into Narnia.

While the books don't say precisely how long they were in Narnia for, nor exactly when in that timeframe The Horse and His Boy takes place, it is clear from Chapter Four that it was not early on:

And if you’ve read a book called The Lion, the Witch and the Wardrobe you may like to know that this was the very same Faun, Tumnus by name, whom Queen Susan’s sister Lucy had met on the very first day when she found her way into Narnia. But he was a good deal older now for by this time Peter and Susan and Edmund and Lucy had been Kings and Queens of Narnia for several years.

So how exactly did they go from frequently discussing it to not remembering it all? Was it just magically wiped from their memories at some specific moment? Or is this merely an inconsistency introduced by a later book?

Answer 1

As noted in the question, it is clear that during the events described in The Horse and His Boy (THaHB), the Pevensies had been ruling Narnia for some time. Lewis points out that they had been “Kings and Queens of Narnia for several years”, sufficient time for Susans to grow from a schoolgirl to a beautiful woman - old enough to be courted by Prince Rabadash - for she and Edward to be described as “grown up, but young”, that is to say, young adults, and for them to have changed to speaking Ye Olde Englishe, also seen at the end of The Lion, The Witch, and the Wardrobe (TLW).

This vague “several years” can be made more precise by consulting the Outline of Narnian history so far as it is is known (available on the Narnia Fandom Wiki), a document used by Lewis which was published after his death by Walter Hooper in Past Watchful Dragons. This reveals that THaHB was set 14 years after the Pevensies entered Narnia, and just one year before they returned to England. The events of THaHB thus happened in the final year of their reigns, and so the “forgetting” of their past lives presumably occurred in that narrow interval of time.

This is not commented on within the Chronicles of Narnia, and I do not believe that the matter is mentioned in Lewis' Collected Letters. In universe, the reader must simply accept the facts as described - that at some point during their final year in Narnia the Pevensies’ memories faded for some reason, presumably some ineffable purpose of Aslan. The more probable explanation, however, is the Doylist view, which is that Lewis simply slipped up here, and when writing THaHB had forgotten about the Pevensies’ loss of memories in TLW. Lewis wrote the Narnia books very rapidly: TLW was submitted to the publishers in July 1949, and Prince Caspian, The Voyage of the Dawn Treader, and THaHB were completed by mid 1950. Writing three complete novels within a year, on top of his other writing and teaching duties, mean that the books were written very “hastily” (in Tolkien’s words). Indeed it is possible that THaHB was written in less than five weeks. Under such time pressure, it is not just possible, but probable that minor inconsistencies will arise. This is commented on by Humphrey Carpenter in The Inklings, describing why Tolkien disliked the Narnia stories:

[Tolkien] judged stories, especially stories in this vein, by severe standards. He disliked works of the imagination that were written hastily, were inconsistent in their details, and were not always totally convincing in their evocation of a 'secondary world'

"The Lion, the Witch and the Wardrobe" offended against all these notions. It had been very hastily written, and this haste seemed to suggest that Lewis was not taking the business of 'sub-creation' with what Tolkien regarded as a proper seriousness. There were inconsistencies and loose ends in the story, while beyond the immediate demands of the plot the task of making Narnia seem 'real' did not appear to interest Lewis at all. Moreover, the story borrowed so indiscriminately from other mythologies and narratives (fauns, nymphs, Father Christmas, talking animals, anything that seemed useful for the plot) that for Tolkien the suspension of disbelief, the entering into a secondary world, was simply impossible. It just wouldn't 'do', and he turned his back on it.