Marissa Thomas: The PwC Powerhouse Redefining the Future of Consulting

Marissa Thomas is one of the most influential figures in the UK professional services and consulting landscape. With more than three decades at the highest levels of PwC UK and now serving as Chief Executive Officer of Unity Advisory, she represents a new generation of leadership that blends deep technical expertise, strategic vision, and modern values such as diversity, innovation, and ethical advisory practice.

Her transition from the Big Four to leading a private-equity-backed challenger firm marks a defining moment not only in her career but also in the wider UK consulting industry.

Marissa Thomas Age and Early Background

Marissa Thomas was born in October 1969, which makes Marissa Thomas age 56 as of 2026.

Although she maintains a private personal life, her professional journey reflects discipline, consistency, and long-term commitment—qualities that have shaped her reputation as a trusted leader in UK corporate advisory circles. She is British, based in Richmond upon Thames, England, and has spent the majority of her career advising some of the most sophisticated investors and organisations in the world.

Marissa Thomas at PwC: A 31-Year Legacy of Leadership

Joining PwC and Rising Through the Ranks

Marissa Thomas joined PricewaterhouseCoopers in September 1993, beginning what would become a 31-and-a-half-year career at one of the world’s most prestigious professional services firms. Over time, she became a partner for more than 21 years, a milestone achieved by only a small percentage of professionals.

Her career progression was not linear by chance—it was built on sustained excellence, client trust, and the ability to lead at scale.

Managing Partner and Chief Operating Officer, PwC UK

The pinnacle of her PwC career came when she was appointed Managing Partner and Chief Operating Officer of PwC UK, one of the firm’s most senior leadership roles.

In this position, Marissa Thomas:

• Oversaw large-scale operational strategy

• Managed complex governance structures

• Led thousands of partners and employees

• Balanced regulatory, commercial, and ethical responsibilities

Her role placed her at the centre of PwC UK’s decision-making during a period of significant transformation in the consulting and professional services sector.

Head of Deals and Head of Tax: Strategic Expertise at the Highest Level

Before becoming COO, Marissa Thomas held two of PwC UK’s most influential practice leadership roles:

Head of Tax, PwC UK

As Head of Tax, she led advisory work on:

• Domestic and international tax structures

• Regulatory compliance

• Complex cross-border transactions

Her work required not only technical precision but also political, regulatory, and commercial sensitivity.

Head of Deals, PwC UK

In her role as Head of Deals, Marissa Thomas advised:

• Private equity firms

• Sovereign wealth funds

• Large multinational corporations

She played a key role in M&A transactions, due diligence, investment structuring, and fund manager set-up, helping clients navigate high-value, high-risk decisions with confidence.

Marissa Thomas and Private Equity Advisory Experience

One of the defining aspects of Marissa Thomas’s professional profile is her deep experience working with private equity investors.

She has advised on:

• Fund formation and operational design

• Acquisition and exit strategies

• Governance and performance optimisation

• International investment structures

This expertise later became central to her post-PwC career, positioning her perfectly to lead a consulting firm backed by global private equity.

Transition from PwC: A Strategic and Defining Exit

In February 2025, Marissa Thomas formally stepped down from PwC after resigning from her partnership and related governance roles. Her departure followed a structured and transparent transition, consistent with UK corporate governance norms.

Rather than signalling retirement, this move marked the beginning of a new phase—one focused on building, not maintaining.

Marissa Thomas as CEO of Unity Advisory

Launching a Challenger Consulting Firm

In May 2025, Marissa Thomas became Chief Executive Officer of Unity Advisory, a new UK-based consulting firm backed by private equity investment.

Unity Advisory was created with a clear mission:

• To challenge the traditional Big Four consulting model

• To operate without audit conflicts

• To deliver advisory services using modern, AI-enabled systems

As CEO, Marissa Thomas is responsible for:

• Strategic direction

• Leadership culture

• Client proposition

• Long-term value creation

A Modern Consulting Model

Under her leadership, Unity Advisory is designed to be:

• 100% advisory-focused

• Free from audit-related conflicts

• Lean and performance-driven

• Aligned with private-equity-style incentives

This approach reflects her belief that the future of consulting lies in agility, transparency, and measurable impact.

Non-Executive Director Role at ECIT

In addition to her CEO role, Marissa Thomas serves as a Non-Executive Director at ECIT, a professional and technology services business backed by TowerBrook Capital Partners.

This role highlights:

• Her governance expertise

• Her credibility with investors

• Her ability to operate at board level across different organisational models

Leadership Style, Values, and Public Voice

Commitment to Diversity and Inclusion

She has consistently spoken about:

• Diversity in leadership

• Creating inclusive professional environments

• Supporting the next generation of talent

Her leadership style is often described as firm but human, combining commercial realism with empathy and integrity.

Personal Values

On her public professional profile, she openly references:

• Her children

• Her passion for diversity

• Her relatable interests, including trainers and everyday life

This balance between senior leadership and authenticity has strengthened her public credibility.

Marissa Thomas in the Context of UK Consulting’s Future

The rise of Unity Advisory under Marissa’s leadership reflects a broader shift in the UK consulting industry:

• Senior leaders leaving legacy firms

• Private equity backing new advisory platforms

• Demand for conflict-free, technology-enabled consulting

Her career symbolises this transition—from traditional structures to future-ready models.

Quick Info

Conclusion

Marissa Thomas is not simply a former Big Four executive; she is a strategic architect of the next era of UK consulting. From her 31-year career at PwC UK to her current role as CEO of Unity Advisory, she has demonstrated resilience, adaptability, and vision.

At 56 years of age, Marissa Thomas continues to shape the industry at the highest level, proving that leadership is not about titles alone, but about the ability to evolve, challenge norms, and build something lasting.

Her journey stands as a compelling case study in modern executive leadership—and her influence on UK professional services is far from over.

FAQs

1. Who is Marissa Thomas?

Marissa Thomas is a senior UK business leader and the Chief Executive Officer of Unity Advisory. She is best known for her long career at PwC UK, where she served as Managing Partner and Chief Operating Officer, making her one of the most senior leaders in the firm’s history.

2. How old is Marissa Thomas?

Marissa Thomas was born in October 1969, which means Marissa Thomas age is 56 as of 2026.

3. What was Marissa Thomas’s role at PwC UK?

At PwC UK, Marissa Thomas spent over 31 years and was a partner for more than 21 years. Her senior roles included Managing Partner and COO, as well as Head of Deals and Head of Tax, where she advised private equity firms, sovereign investors, and large corporate clients.

4. What is Unity Advisory and what does Marissa Thomas do there?

Unity Advisory is a private-equity-backed UK consulting firm designed to challenge the traditional Big Four model. As CEO, Marissa Thomas leads the firm’s strategy, culture, and growth, focusing on conflict-free, advisory-only services supported by modern, AI-enabled delivery models.

5. Is Marissa Thomas married?

Marissa Thomas keeps her personal life private. While she has publicly mentioned her children, no verified public information is available about her husband or marital status.

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