10 Times Doctor Who Has Broken Its Own Rules
6. Time Lord Detection
With so few of his species left in existence, and thought to be the last of the Time Lords throughout most of NuWho's early days, you would think the Doctor's ability to know his own would be more consistent.
2007's The Sound of Drums stated that the Doctor would instantly recognise one of his own people, but the Master's surprise appearances since have consistently disproven this conclusion. On the run, the Tenth Doctor told his companions that when he saw the Master, he'd know him straight away - a gift of the Time Lords. But what about Missy? And the 'O' Master, who first appeared in 2020's Spyfall?
Unable to detect Professor Yana in Utopia due to his biodata being concealed by a Time Lord fob watch, this surprise appearance made sense - but why couldn't the Twelfth Doctor work out who Missy was in 2014's Dark Water? Likewise, O's secret identity shouldn't really have been so secret if the Doctor really did have Time Lord detecting powers.
Like Professor Yana, the 'Fugitive' Ruth Doctor pulled the wool over the Doctor's eyes by concealing her identity within a fob watch, but no narrative reason has been provided for why Missy and O completely slipped under the radar.
These rule breaks, and the Doctor being in the dark, should probably just be put down to 'plot twists'.