- You may be looking for the anthology Old Friends.
Old Friend was the fourth and final comic story in the Doctor Who Annual 2010.
The Tenth Doctor and Emily exit the TARDIS into a house for the elderly. They are met with suspicions by the head nurse. They claim to have come as a "surprise inspection". In the house's main hall, a small party is being thrown for Barnaby Edwards, one of the residents, who recognises the Doctor and asks to talk to him.
Barnaby tells of how he recognised him, in spite of being a companion of a future Doctor. That Doctor gave him an envelope to hand to his earlier self. He also mentions encounters with Sontarans and "the Floor Menace" and profusely apologises for leaving the TARDIS; he had fallen in love and felt he had to live his own life.
The Doctor assures him he had been "one of the best companions ever" and he does not nurse any anger towards him for leaving the TARDIS. The relieved Barnaby sighs in relief and goes to sleep as the Doctor leaves. Emily tries to tell the Doctor something about Barnaby, but the Doctor stops her, saying he doesn't want to know.
Opening the envelope within the TARDIS, the Doctor finds a single, charred sheet of paper-one of the pages of the false diary supposedly kept by Turlough. Realising the message was that the diary was to be soon destroyed, the Doctor changes course to meet with the Advocate and ensure her final defeat.
- The Doctor and Barnaby encountered the Sontarans during their travels together.
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