Banham are really a London-based locksmith/installer company.
They designed and patented their own locks, but (as is a common practice in many industries), not having their own production capability, they contracted with a company which did, to make Banham locks for Banham's exclusive use. That company was Erebus.
In recent years, production has moved to Guardian Lock & Engineering Co. They have sophisticated CAD design capability and are good at designing and making short-run specials for anyone. In concert with Banham, Guardian Locks now do most of the new designing for Banham, as well as production, to Banham's requirements. But the locks are still Banham locks.
Guardian also make locks for several other companies.
Their trade mark is Imperial Locks, and their motto is 'We make locks'.http://www.imperiallocks.co.uk/about.htm