The cast of 'Downton Abbey' have been posing for promotional photos ahead of the fifth series starting on ITV and some eagle-eyed fans have spotted a not-so-deliberate mistake in one of the pics.
Despite the new series being set in 1924, in one shot of the Earl Of Grantham (Hugh Bonneville) and Lady Edith Crawley (Laura Carmichael), a plastic water bottle can clearly be seen on the mantlepiece behind them.

Whoops.
And if you didn't know already, plastic bottles like the one over the left shoulder of Lady Edith, weren't even a thing until the early 1960s.
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