In real life, Sir Ian McKellen and Dame Helen Mirren are close neighbors, they both live in Wapping, in East London.
The Charing Cross station used in this movie is the closed Charing Cross station on the Jubilee Line. It was used in Skyfall (2012).
Sir Ian McKellen starred in another New Line Cinema production The Lord of the Rings: The Fellowship of the Ring (2001) as Gandalf the Grey. His first line in this film is, "Don't tell me I'm late, I'm never late," a nod to his first lines in The Lord of the Rings: "A wizard is never late, Frodo Baggins. Nor is he early. He arrives precisely when he means to."
When Vincent explains what he does he references the Inland Revenue even though this was replaced by HMRC in 2005. This is a common mistake still made by some people even now.
Though Dame Helen Mirren and Sir Ian McKellen star together for the first time in a movie, they had previously played characters Alice and Edgar in playwright August Strindberg's "Dance of Death" in New York (2001-2002).