Remember the Lego Tube maps Transport for London commissioned as part of the network's 150th anniversary? Well, by way of a little Easter egg, tucked away on TfL's website is a recipe for building your own standing tube roundel from the popular plastic bricks.
The PDF file gives step-by-step instructions for using one icon of design (Lego) to build another (the roundel). The instructions require some relatively arcane bricks, including 18 cylinder pieces and some weird curvy pieces, but we're sure enthusiasts can track the components down.
If anyone's actually made one, do send us a photo of the creation in some kind of appropriate setting.
With thanks to the ever eclectic Reddit London page for the tip-off.