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Bill Nighy agreed to take the part on condition that he was not credited, no publicity photos were taken of him, and he did not have to give any interviews.
After the broadcast in the UK, a special announcement broadcasting a suicide prevention number was made.
Bill Nighy had previously been rumoured as a candidate for the Ninth or Tenth Doctors. He joked that he lost the latter because David Tennant was better looking.
The self-portrait of Vincent van Gogh is not an exact replica; it is altered slightly to resemble Tony Curran, the actor who plays Vincent. This painting would later show up as an image in an historical archive in Smile (2017).
The producers have stated that they cast someone as high profile as Bill Nighy for such a small part was because they needed the audience to listen to what the character said (which in this case were important biographical information about Vincent).
Richard Curtis had been fascinated by the life of Vincent van Gogh. Though it was a subject he knew "quite a lot" about, he still read a 200-page biography of Van Gogh, which was more research than he normally would have done if working on other projects; he took Van Gogh very seriously. As such, he wanted to be "truthful rather than cruel" and refused to write any jokes about Van Gogh's ears after he famously cut one of them off.