BBC is investigating if Russians leaked Sherlock finale

The BBC is investigating how the fourth season finale of Sherlock was leaked online, after a Russian-language version of the episode was illegally uploaded ahead of transmission.

A leaked version of His Final Problem featured a short continuity announcement that identified it as broadcast by Russian state-owned Channel One. It appeared online on Saturday.

After the leaked episode started circulating online, the BBC tweeted:

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The show's producer Sue Vertue confirmed the leak originated in Russia and appealed users not to share it:

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The BBC later confirmed in a statement that it is conducting an investigation into the leak.

"BBC Worldwide takes breaches of our stringent content security protocols very seriously and we have initiated a full investigation into how this leak has occurred," it said.

Mashable understands that the British broadcaster is in contact with Channel One in Russia to understand what has happened. It will make a statement once the inquiries are concluded.

Many UK newspapers suggested the hack could have political motives. The Daily Telegraph reported claims that the Kremlin was angered by a recent decision to expand the BBC World Service's Russian language output.

In October, a spokeswoman for Russia's foreign ministry promised tit-for-tat retaliation against British media after NatWest attempted to close bank accounts linked to RT, Russia's English-language broadcaster.

“Our stance is straightforward: we will stick up for our own," Maria Zakharova said. "They [Britain] will get as good as they give."