This movie is the property of the BBC (they make very good stuff, check them out!)
Not sure which one is it, irish or scottish.
When I say "best accent" I mean that I consider his play in this scene as a great one. You may find it not amazing.
Sherlock S04E03
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Sherlock [2010, 2012, 2014, 2016, 2017]
Creators: Mark Gatiss, Steven Moffat
Writers: Mark Gatiss, Steven Moffat, Arthur Conan Doyle, Steve Thompson
Directors: Nick Hurran, Rachel Talalay, Benjamin Caron [2017]
Actors [in this scene, not all of them]: Benedict Cumberbatch, Mark Gatiss, Martin Freeman, Art Malik
I don't know who the security guards are, so if you know them, let me know