Minor nitpick: inline assembly had been invented already. Indeed it had been implemented and shipped for the Acorn Atom in 1980. The Atom packed a quirky but effective BASIC with an inline 6502 assembler into its 8Kb ROM. And a BASIC with rather more features, and an inline assembler, was shipped with the BBC Micro, slightly ahead of the ZX Spectrum launch. Folks on the Cambridge scene had the chops to do better versions of BASIC, they just didn't make it into any Sinclair products until the QL. (And, a later Sinclair product, the Z88, of course, shipped with the Z80 version of BBC Basic a few years later, this time with an inline Z80 assembler.)