Getting helmet sizing right starts with a proper head measurement, taken with a soft tape around the largest part of the head, just above the eyebrows and ears. That figure points to a starting size, but it is only a starting point, since head shape varies as much as head size.
A made to order helmet starts long before any material is cut. Measurements are taken, the intended use of the helmet is discussed, and a rider works with the maker to settle on a shell, lining and finish that suit them specifically, rather than picking from fixed stock sizes.
Certification is not a formality. It is the baseline that separates a genuine protective helmet from something that only looks the part. Any helmet worth wearing on the road should carry a current, verifiable certification.
To browse current models when it is time to replace yours, see
Hedonist.
From there, the build follows the same certified construction as the standard range. Made to order does not mean a shortcut around testing, it means the standard process is carried out around one person's measurements and preferences instead of a general size run.
A helmet workshop in London works on a smaller scale than a mass production line, and that shapes almost everything about how a helmet gets made. Materials are chosen and checked by hand, shells are shaped and finished in small batches, and problems are caught by people who see every stage, not just a sensor on a line.