This episode is based on the seventh novel in "The Cadfael Chronicles", which was published in 1983.
Hugh Bonneville (Daniel Aurifaber) and Derek Jacobi (Brother Cadfael) have both played Edward Masterson in adaptations of the 1934 novel "Murder on the Orient Express" by Agatha Christie: Bonneville in Murder on the Orient Express (2010) and Jacobi in Murder on the Orient Express (2017).
Hugh Bonneville and Toby Jones also appeared in the same episode of Agatha Christie's Poirot - Murder on the Orient Express.
Hugh Bonneville (Daniel Aurifaber), Derek Jacobi (Brother Cadfael), and Toby Jones ( ) have all appeared in the Dr Who series.