AI prompt engineer/ Agent builder (Claude) in London

At Grant Thornton we’re building something bold. We’re doing things differently - looking to the future, driving ambitious growth and pioneering positive change in our industry. Providing audit, tax and advisory services, we empower clients through strategic insight, curiosity, and genuine partnership. And we empower our people with real opportunity. Our journey from great to exceptional is well underway. With significant investment behind us and a clear strategy for growth, there’s real momentum.

Our Agile Talent Community (ATC) brings together experienced contract professionals who want choice without losing connection. You work where you add the most value, alongside teams who treat you as a partner rather than a placeholder.

Grant Thornton's Marketing function is delivering an ambitious AI transformation programme — building a suite of Claude-powered agents that automate and augment the full marketing workflow, from brief writing and content production through to campaign measurement and optimisation. We’re looking for a hands-on AI builder to join the team and turn problem statements into working tools, fast.

If you’re an experienced AI prompt engineer / Agent builder, you’ll take scoped agent briefs and build production-ready Claude-powered tools — designing prompt architecture, testing against real marketing scenarios, iterating based on feedback, and documenting what you’ve built so the team can maintain and extend it. You’ll work across multiple agents simultaneously, managing your own prioritisation within a defined delivery roadmap. You’ll be given the opportunity to take on short- to medium-term projects that sharpen your expertise, stretch your thinking, and give you a different angle on familiar challenges - all without locking you into a single path.

You can engage with us through your own limited company or on inside IR35 terms - whichever way gives you the freedom you’re looking for.

Skills we are looking for:

• Proven experience building with Claude or comparable LLMs — not theoretical, demonstrably shipped
• Strong prompt engineering skills: system prompts, chain-of-thought design, output structuring, guardrails and escalation logic
• Ability to read a problem statement and move to a working prototype without needing the brief to be perfect
• Experience working in marketing, content, or communications contexts is a strong advantage
• Comfortable working at pace in a delivery-focused environment with real stakeholder visibility

Why Consultants choose the ATC:

• Work that moves you forward: When a project fits your skills, we’ll get in touch, but you choose whether it’s right for you. That means working on engagements that genuinely build your portfolio and expand your expertise.
• The freedom of contracting without the hidden admin: You’re not left to navigate the freelance world alone. Our Agile Talent team helps you understand freelance regulation and connects you with people who broaden your thinking through our teams and clients.
• Community you can actually feel: Connection shouldn’t disappear just because you’re contracting. From market insights to wellbeing sessions to networking events, you’ll be part of a community designed to make the independent path less isolated and more impactful.

Our culture and values:

We have a culture where talented people thrive – where high performance is not just expected but enabled. It’s a culture built on clarity, curiosity, and care. One that challenges us to aim higher, where we’re encouraged to make the most of an abundance of resources to fuel our own development, and where we support each other to grow, learn, and succeed.

Our open and accessible culture means you’ll interact with leaders who are interested in you and everything you bring to our firm. The things that set you apart, we value them. That’s why we give you the freedom to bring your whole self to work and pursue your passions inside and outside of work.

How to join:

We keep the process straightforward, because the real work happens once you’re here. Submit your CV and basic details through our online application. If there’s a match, a recruiter will reach out to discuss. Meet key stakeholders for a focused conversation. Complete your background checks, join the Agile Talent Community, and start exploring the opportunities we have to offer. If you need adjustments at any point in the process, please let us know during the application stage - we aim to make sure our roles are accessible to everyone.