Founding Head of Public Sector in London

Location: London; 4 days in-office, 1 day wfh

Reports to: Chief Commercial Officer

Cosine is the UK's frontier AI lab for autonomous software engineering. We build our agent tooling entirely in-house and post-train open-source models to deliver reliable, enterprise‐grade coding performance in security‐critical settings. Our offerings can be used as SaaS, deployed on VPC, on‐prem or fully air‐gapped. Through this flexibility, we are able to service large‐scale, highly regulated enterprises and industries including defence, financial services and healthcare. We're backed by YC and were recently selected for the UK's sovereign AI programme.

Mission: Own Cosine's public sector engagement and GTM motion from founder‐led relationship building into a repeatable commercial engine. The role exists to build on Cosine's growing reputation across government, defence‐adjacent bodies, public sector technology teams, and the wider UK sovereign AI ecosystem, turning senior interest into deep institutional relationships, clearly understood priorities, and qualified commercial opportunities.

This is a critical sector‐building role: part enterprise sales, part partnerships, part market development, part public sector navigation, and part GTM leadership.

Core responsibilities:

• Lead engagement with public sector organisations and priority accounts.
• Build multi‐threaded senior relationships.
• Build Cosine's understanding of public sector sovereign AI priorities.
• Build towards commercial opportunities.
• Work closely with systems integrators and delivery partners.
• Navigate public sector routes to market.
• Help build the GTM team in public sector.

What good looks like in the first 6 months:

• Multi‐threaded relationships established across the most important public sector accounts.
• A structured view of public sector sovereign AI use cases, buyer priorities, objections, procurement routes, SI influence, and buying triggers.
• Qualified opportunities progressing into discovery, technical deep‐dives, pilots, bid discussions, partner motions, or commercial proposals.
• A clear public sector GTM playbook that future hires can build from.

Success metrics:

• Number of priority public sector accounts actively engaged.
• Number of senior stakeholder relationships built across target accounts.
• Quality of customer insight captured on sovereign AI priorities, deployment requirements, procurement constraints, and use cases.
• Qualified public sector opportunities created.

Candidate profile:

This role is likely to suit someone who:

• Has sold, partnered, or built relationships inside public sector, government, regulated infrastructure, defence‐adjacent markets, or public sector technology programmes.
• Understands how public sector organisations buy, including procurement routes, framework dynamics, bid processes, partner influence, and the role of SIs.
• Can credibly engage senior stakeholders while still doing the account‐by‐account follow‐up work themselves.
• Is comfortable working with SIs, consultancies, and delivery partners without losing sight of Cosine's own commercial interest.
• Thinks commercially, writes clearly, and can build account plans, briefing notes, proposals, bid inputs, and internal decision materials without heavy supervision.

Summary: The Founding Head of Public Sector should make Cosine impossible to ignore for the right public sector organisations. They should build on Cosine's growing reputation in sovereign AI, understand what these institutions actually need, build the relationships required to be taken seriously, and work closely with systems integrators and the Head of Partnerships to create credible routes into bids and programmes.

Why join Cosine:

• Opportunity to sell a genuinely differentiated product into mission‐critical defence and national security environments.
• Meaningful early equity with real upside.
• Direct impact on product direction and go‐to‐market strategy.
• Small, elite team with high standards and strong technical depth.

What you can expect:

• Competitive salary, benchmarked to the market.
• Equity / share options, so you share in the upside you help create.
• 30 days' holiday + bank holidays.
• Dog‐friendly office - bring your dog to work.
• Weekly team breakfast & lunch.
• Monthly socials.
• Pension.
• High‐quality equipment to do your best work.

We're an equal opportunity employer. We value diverse backgrounds and encourage applications from everyone who meets the role requirements, even if you don't tick every box.