When casting the part of Sarah, writer and director Richard Curtis auditioned a great many British women, but kept saying, "I want someone like Laura Linney." The casting director eventually snapped and said, "Oh, for fuck's sake, get Laura Linney then." Linney then auditioned and got the part.
The airport greeting footage at the beginning and end of this movie is real. Writer and director Richard Curtis had a team of cameramen film at Heathrow airport for a week, and whenever they saw something that would fit in they asked the people involved for permission to use the footage.
The lake in which Lúcia Moniz and Colin Firth are "swimming" was actually only eighteen inches deep and they had to kneel down and pretend to be in deeper water. It was also over-run by mosquitoes. Colin Firth was badly bitten and his elbow swelled up to the size of an avocado, requiring medical attention.
A speech given by Hugh Grant in this movie (where he extols the virtues of Great Britain and refuses to cave to the pressure of its longstanding ally, the United States) was etched in the transatlantic memory as a satirical, wishful statement on the concurrent relationship with George W. Bush. Tony Blair responded by saying in 2005, "I know there's a bit of us that would like me to do a Hugh Grant in Tatsächlich... Liebe (2003) and tell America where to get off. But the difference between a good film and real life is that in real life there's the next day, the next year, the next lifetime to contemplate the ruinous consequences of easy applause."
The idea for Mark's (Andrew Lincoln's) surprise of the band singing "All You Need Is Love" at Peter (Chiwetel Ejiofor) and Juliet's (Keira Knightley's) wedding came from Jim Henson's funeral (which writer and director Richard Curtis attended) where all of the puppeteers brought their Muppets and sang a song.