As a big fancy Hollywood star of blockbusters like the X-Men franchise and It Chapter Two and also the proud owner of a charming Scottish accent, James McAvoy has to work hard to keep that burr out of his voice when he's playing Brits and small-town Americans.

But as he explains to Stephen Colbert during his appearance on The Late Show on Wednesday night, there's one word too full of Rs for even his professional expertise: "Burglary." Watch him dissolve into giggles around 6 minutes into the above clip.

While he can't choke it out even in his own accent, he's also got a spot-on impression in his pocket of BFFs Sir Ian McKellen and Sir Patrick Stewart, aka "Sirs Squared", for a story towards the end of the clip that's pure delight.