Yes! This is a woodlouse.It's very well camouflaged on the pavement! We can't really say which species as the image is too blurry, unless anyone else has an informed opinion!
Woodlice do look prehistoric, it's true, and they are considered primitive. It's interesting you found it on the quayside, as taxonomically, woodlice belong to a group of arthropods called the Crustacea which includes the crabs, lobsters and shrimps. Isopods (the woodlice) and another order, the Amphipoda, are the only Crustacea that do not require water as part of their life-cycle development.
There are 37 species of woodlice in Britain - which one is yours I wonder!
The quayside and the size gives me a clue - this will almost certainly be the common Sea Slatter, Ligia oceanica. This is the UK's largest 'woodlouse' and found exclusively near marine environments. It's a beauty, and quite nippy too.