10 MORE Important Doctor Who Details That Are Almost Never Mentioned

In City of Death, some timey-wimey shenanigans have resulted in the alien Scaroth being split into 12 telepathically-linked people scattered throughout human history.

In desperate need of some cash to fund his attempts to reverse these shenanigans, he uses his fractured selves to his advantage, with his 16th century splinter approaching Leonardo da Vinci and convincing him to paint six copies of the Mona Lisa. In the present day, he steals the “original” painting from the Louvre, and intends to sell all seven versions on the black market, with each buyer thinking they have the real, original version.

True to form, the Fourth Doctor has an equally ingenious plan to stop Scaroth: he travels back in time and writes “THIS IS A FAKE” on the canvasses for the six Mona Lisa copies. Eventually, a fire destroys all but one of these Mona Lisas, which is returned to its normal place in the Louvre.

This doesn’t seem like a big deal at first – after all, da Vinci did still paint the duplicates, and he did paint over the "THIS IS A FAKE" message – but it leaves a ticking time-bomb in present-day Earth. If discovered, this message would create doubt over the authenticity of arguably the single most famous painting in the world, and further still, this painting now holds undeniable proof that somebody in the 16th century was running around with a felt-tip pen!

It's also fun to imagine that when the Spy Master defaces the Mona Lisa and when the painting comes to life in The Sarah Jane Adventures, that's actually one of da Vinci's "fakes". The news would have an absolute field day if the truth was ever discovered!