Double, Double Toil and ...

Double, double toil and trouble;
Fire burn, and caldron bubble

It's all down to the punctuation, although that can get lost in the street art format.

A bit of a variation on my earlier Street Art blips but thought this was appropriate given the location and timing - positioned right opposite the High Court in Parliament Square and just when there's lot of Shakespeare coverage on radio & TV!

Oh no, silly me - it's not Shakespeare but JK R & 'Arry Potter!
- although different punctuation!