Doctor Who: Ranking The Weddings Of The Whoniverse
5. Sarah Jane Smith And Peter Dalton (The Wedding Of Sarah Jane Smith)
Luke, Rani, and Clyde are initially happy for Sarah Jane when she becomes engaged to a seemingly normal man named Peter Dalton. However, the kids begin to suspect Peter is not as he seems when Sarah Jane begins acting strangely after the engagement.
They are proved right when The Tenth Doctor arrives, revealing that Peter is a pawn of Sarah Jane's long time enemy The Trickster. Revived by The Trickster after a fatal fall, the villain offered Peter a chance to find love. However, Peter never knew that The Trickster's real plan was to draw Sarah into a time loop where we could strip her memories of all her adventures.
Peter sacrifices his second chance at life to save Sarah Jane, leaving poor Sarah heartbroken. Sarah's wedding is notable for being the last story David Tennant filmed as the Tenth Doctor.