What is a Hallmark?
It has been a centre of expert opinion and independent assessment of jewellery and precious metals for nearly 250 years. Read More Here
TLDR; Hallmarking assures that the precious metal item you are buying is legit and you should always keep an eye out for it.
The law applies to everything sold in the UK, regardless of where it may have been manufactured. However there is an exemption for silver items under 7.78 grams.
I hallmark each of my items, regardless of their weight as I find because I hand make everything it adds an extra bit of assurance.