A clean combination logo that is just as clever as the company name itself.
The negative space inside the icon creates the letter Q from the wordmark. The icon itself is actually comprised from the negative space around the Q in the wordmark, which also resembles the roman numeral LI or 51. The icon as a whole, alludes to "LI Q" aka "51 Q" aka "51 Quid".
In the wordmark, the Q from the icon is present and the rest of the type is designed to work with it, keeping everything simple and cohesive.