A question of Marks ?

[Prydonian]

Well, the basic costume they supplied Tom with for Season Eighteen had a more uniform feel than his earlier costumes. JN-T apparently liked having his leads wear uniform-looking outfits, take a look at pics from Season Nineteen where the Doctor and all his companions are thus adorned. Every Doctor after Tom in the classic series would later complain to some degree about the costumes that they were forced to wear.