Client Success Partner (12-month FTC)

A commercially astute and consultatively minded Client Success Partner to join our client leadership team. This is a senior advisory role at the heart of how we create value for our clients — translating complex analytical work into strategic guidance that directly shapes our clients' investment decisions and growth trajectories. 

You are a trusted advisor first and foremost — someone who builds genuine partnerships with senior client stakeholders, earns a seat at the table through deep expertise, and brings the intellectual curiosity and commercial instinct to identify where Gain Theory can make a meaningful difference. 

You will bring 12+ years of experience in marketing effectiveness, analytics, or a related consulting discipline. 

• Acting as a Strategic Advisor to Senior Clients: You'll be the primary consultative voice for your clients — proactively shaping how they think about marketing investment, effectiveness measurement, and growth. You won't wait to be asked; you'll bring forward-looking perspectives, challenge assumptions constructively, and connect analytical findings to real business outcomes. Your clients will value you as a partner who understands their world as much as you understand ours. 

• Translating Complexity into Strategic Clarity: You'll take sophisticated analytical outputs (MMM, attribution-like techniques), scenario planning) and craft compelling narratives that resonate with senior decision-makers. Your ability to distil complexity into clear strategic recommendations will be central to the value clients associate with Gain Theory. 

• Shaping the Consulting Agenda: You'll lead strategic client conversations, facilitate workshops, and contribute to thought leadership that keeps Gain Theory working at an elevated level with our clients. You'll bring genuine intellectual curiosity to your clients' industries, anticipating trends and advising on where measurement and investment strategies need to evolve. 

• Identifying and Developing Client Opportunities: Through deep understanding of your clients' challenges and ambitions, you'll proactively identify where expanded consultancy can add value — growing relationships organically through relevance and trust. You'll lead new business conversations and pitches with authority and credibility. 

• Enabling a High-Performing Consultancy Team: You'll lead and mentor a team of five (plus broader dotted-line relationships), fostering a consultative culture built on intellectual rigour, client empathy, and continuous learning. You'll ensure delivery quality remains high while developing your team's ability to think and communicate like trusted advisors. 

• Analytics Consultancy Expertise: A proven track record of advising senior stakeholders, framing complex problems, and delivering recommendations that influence real strategic decisions. 

• Deep Analytical Fluency: The ability to engage meaningfully with sophisticated analytical methodologies such as MMM, lift tests and attribution, translating them into clear, actionable strategic narratives for non-technical audiences. 

• Trusted Relationship Building: Demonstrated success in developing genuine, long-term advisory relationships at C-suite and senior marketing leadership level — built on credibility, candour, and consistently delivering value. 

• Strategic & Commercial Acumen: Experience identifying growth opportunities through consultative insight, with a strong understanding of how to articulate and demonstrate value in a professional services context. 

• Industry Knowledge & Intellectual Curiosity: Deep grounding in marketing effectiveness and analytics, combined with a genuine interest in clients' industries and an ability to connect broader market trends to client-specific challenges. 
• Values Alignment: A natural alignment with core values: Be Curious, Be Positive, Act with Consideration, and Make it Better. 

Your Impact Will Be Measured By: 

• Depth and quality of strategic advisory relationships with senior client stakeholders 

• Demonstrable value and strategic influence delivered to clients 

• Exceptional client satisfaction (Performance, Preference, Likelihood to Recommend) 

• Achievement of net sales growth targets through consultative opportunity development 
• High satisfaction and consultative capability growth within your Client Success team 

Key Relationships You'll Build: 

• Senior client stakeholders (Marketing Directors, CMOs, Insights and Strategy leads) 

• Client Success Group & Executive Leadership Team 

• Gain Theory's Data, Analytics and Operations community, plus New Business and Strategy teams 

Location: 

Ideally London, with an expectation of 2–3 days in Gain Theory and/or client offices. 

Gain Theory is committed to actively building a diverse, equitable and inclusive workplace where everyone feels welcomed, valued and heard, and is treated with dignity and respect.  As leaders and creative partners across industries, it is our responsibility to cultivate an environment reflective of our greatest asset; our people. We believe that this commitment inspires growth and delivers equitable outcomes for everyone as well as the clients and communities we serve. 

• Growth and development
• Meaningful work
• Flexible by design
• Brilliant benefits 
• Culture with Heart

Our exceptional and skilled team defines Gain Theory. That's why we seek individuals who strive for excellence and continually challenge us to improve.

Gain Theory is a global marketing effectiveness and foresight consultancy. Our vision is to accelerate growth for ambitious brands by giving clients the confidence to make better data-informed investment decisions. High-touch consultancy powered by unique partnerships and proprietary technology are used to power our award-winning solutions.  

 As a WPP consultancy, Gain Theory also has access to a range of data, expertise, and tools that create a truly differentiated offering. 

 Gain Theory is a WPP agency (NYSE: WPP).      

We are a people-centric organisation whose culture is underpinned by 4 important values: Be Curious, Be Positive, Make it Better and Act with Consideration. We channel these values through our behaviours, in the way we work, and in the interactions we have with each other and our clients.