Top Tech Startups in Greater London, United Kingdom in 2027

SalesCaptain is a top-ranked outbound and GTM agency helping B2B companies like Nestlé Professional, Drip, Robin AI, Persado, and GlossGenius scale their sales pipeline. We combine AI-led outbound, GTM transformation, and RevOps implementation to drive meetings with in-market buyers.

AI credit analyst for business lending and credit teams

Mercor partners with leading AI labs and enterprises to train frontier models using human expertise. With a talent network of more than 30,000 people across hundreds of domains, Mercor is building a new category of work where expertise powers AI advancement. While computing power and engineering talent have advanced rapidly, AI models can only improve when they learn from real human expertise across disciplines like law, medicine, coding, and finance. Mercor bridges this gap by connecting top professionals with frontier AI labs, enabling them to share insights, provide expert feedback, and shape the reasoning capabilities of next-generation models. Backed by $350 million in Series C funding led by Felicis, with Benchmark, General Catalyst, and Robinhood Ventures, Mercor is now valued at $10 billion. At its core, Mercor’s culture thrives on impact, agility, and growth. Mercor powers its teams to build at the frontier of technology.

What are we building? Software was supposed to help us. Instead, it swallowed the working day. Everywhere you look people are buried under the burden of software. We are starting with automating email, turning it from a burden into a powerful competitive edge for people who grow businesses and build a reputation in their inbox. Think real estate, consultants, recruiters - people who spend hours on emails, scheduling, and follow ups. Unlike other startups, we're a pure-play applied AI company and not a SaaS company with AI features hastily bolted on. We use the best techniques (fine-tuned open-source models, tool use, and retrieval-augmented generation), and as a result, users send 53% of the email drafts we generate. How has it been going? From $1M to $25M ARR in the last 10 months, making us the fastest growing startup ever in the UK. We are backed by top-tier investors including: Marc Benioff (Founder of Salesforce), Harry Stebbings (Founder of 20VC), Douwe Kiela (Founder/CEO Contextual AI/Creator of RAG), David Singleton (Former CTO of Stripe), Des Traynor (CTO Intercom), Madrona (First Investors in Amazon/Snowflake). What do we value? We're very intentional about adding new people. We believe a small team of exceptional people working hard at a problem they care about will always outperform a larger, more unfocused team. That means you'll need to bring an intensity to this role that might not be expected at other companies but it also means you'll be fast-tracked into roles with greater responsibilities far earlier.