William Mattey is the founder of Wall & Fifth, a senior-led London software studio that designs and builds custom apps, MVPs, marketplaces, SaaS platforms and AI products for founders and owner-led businesses. He works hands-on across product, engineering and commercial strategy. Every build is scoped, designed and shipped by senior people rather than handed to a junior team. Wall & Fifth works fixed-price, and clients own their codebase outright with no licensing or lock-in. Recent work spans payments infrastructure, native iOS applications, marketplace platforms and white-label brokerage systems deployed across multiple client-owned domains. Wall & Fifth also builds and operates its own products, including sellyourboat.io, a yacht marketplace with an AI-powered search and ...