Why Mark Tietjens decides to remain silent and immobilized - Parade's End

At the end of section 1 of Last Post, the final volume of Ford Madox Ford's Parade's End, FMF gives us a fairly detailed account of Armistice Day in London, this time in sequence from the POV of Mark Tietjens and from his wife, Marie - a French woman who had been is "mistress" but whom he finally marries, as discussed in Mark's interior ruminations about mistresses and prostitutes and kept women and whom a gentleman should marry - he seems to see his marrying her as some sort of benevolence. In any case, what we see on Armistice Day is an account of Christopher Tietjens dunning his brother, Mark, for some money, leaving some crappy furniture as collateral, so that he can spend some time in his long-awaited sexual liaison w/ Valentine Wannop - but of course Mark never gives him the money, and the night gets spent in frustration, his carousing with various war buddies in various states of shell shock, inebriation, and madness. Its almost but not quite comical. Mark provides an insight that had never come up in this novel to this point - the possibility that Valentine and Christopher are half-siblings. Strange indeed. Strangest of all is Mark Tietjens's determination to be silent and immobile - which seems to come about when he learns that the British will not pursue the retreating German army back to Germany. Now it certainly seems odd that such news would drive him to a lifetime of paralysis - perhaps he did have a stroke and his silence is not a willed decision? But in any case I think he's clearly not reacting only or even primarily to this news but to his vision of the collapse of the British way of life as  he knows it, that is, to the class structure, as he sees men socializing together across various class boundaries - the war has created an entirely new network of associations and allowed possibilities - it's this that he's protesting against, that revolts him, that forces his retirement from life itself. There may be an aspect of his anger at Britain's failure to pursue - but I would have thought he'd more likely be a pacifist than a war-monger. More on this perhaps in a later post.