It's a storyline that we imagine would have the servants of the sprawling estate almost hysterical as they tried to get everything ready for the arrival of a Duchess. We don't think Mrs Padmore would survive it, quite frankly.
Lucky then that the show's only fiction, although something tells us that the cast and crew will still have to struggle to keep their cool when Duchess Kate arrives next Thursday 12th March.
But before you get too excited that Kate's going to pull a Clooney and make a cameo in the next series, she is purely there to see where the action takes place – we won't be catching a glimpse of the 32-year-old's acting abilities this time around.
A message from Kensington Palace informed us that 'The Duchess of Cambridge will visit Ealing Studios to celebrate the success of the award-winning production, Downton Abbey, on Thursday 12th March 2015. Her Royal Highness will tour the Downton Abbey set and meet cast and crew members'
However, maybe the Duchess will get into the spirit of things like uber fan Ralph Lauren, who recently took up residence in the house with his family for a short holiday and got dressed up in period costume to take a stroll around the grounds.
If Kate does fancy raiding the wardrobe departmenr, we reckon Lady Mary's most likely still got a couple of maternity dresses knocking around that will fit…