Our Executive Team combines expertise across insurance, underwriting, medico-legal support, finance, governance and corporate services

Driven by a clear vision and shared commitment to our Members, they ensure our services remain robust, relevant, and responsive to Member needs now and into the future.

Tim Plant

Chief Executive Officer

Tim Plant is Chief Executive Officer of MDA National, leading the organisation with a focus on long-term sustainability and Member-focused growth. He brings broad experience across insurance, reinsurance, and financial services.

His leadership has spanned strategy, risk, technical insurance and commercial operations, championing innovation and outcomes that meet the evolving needs of Members and stakeholders.

He also brings deep governance expertise, having served as both Executive and Non-Executive Director across a range of businesses, including APRA-regulated entities. Bringing strategic insight, collaborative leadership, and strong stakeholder engagement, Tim is passionate about shaping the future of insurance and financial services by guiding the business through a new era of best-in-class Member experience.

Steve Sheppard

Chief Operating Officer

As Chief Operating Officer at MDA National, Steve brings extensive operational leadership experience and a strong track record of delivering results in complex and evolving environments. He plays a key role in shaping service performance and operational delivery across the organisation.

Known for his Member-first mindset and collaborative leadership style, Steve effectively motivates teams, drives service innovation, and fosters continuous improvement to enhance Member outcomes. With over 30 years’ experience across the financial services sector, he brings deep commercial insight and an unwavering focus on delivering value through meaningful, measurable change.

Natalie Buffett

General Manager
Technology & Security

Natalie leads the delivery of IT transformation, technology programs, and strategic projects that strengthen MDA National’s digital capability. Her team is focused on enhancing system security, enabling scalable technology solutions, and supporting the organisation’s growth and proposition development.

With expertise in business transformation, technology strategy, governance, and operations, Natalie brings a practical understanding of how to align technology with business goals to deliver meaningful outcomes for Members.

Philippa Nash

General Manager
Claims, Advisory, Risk and Education

Philippa leads MDA National’s Claims, Advisory & Education team, guiding the support we provide to Members when it matters most. With a unique background that bridges healthcare and legal expertise, she works closely with Members, leading medical practitioners and legal experts to deliver responsive, informed support across complex medico-legal matters.

Philippa brings experience from both health and legal sectors, including roles at leading law firms in Australia and the United States. Since joining MDA National, she has become a trusted leader in medico-legal strategy, known for her empathetic approach, depth of insight, and commitment to protecting the professional integrity of healthcare practitioners.

Alison Seinor

General Manager
Risk & Compliance

Alison leads MDA National’s Risk & Compliance function with a strong foundation in financial services, risk mitigation and complex regulatory environments.

Alison plays a pivotal role in shaping governance practices, strengthening risk frameworks, and supporting compliance across the organisation, ensuring MDA National remains resilient, forward-looking, and well-positioned to continue protecting Members nationwide.

Luke Thomson

General Manager
Pricing & Portfolio Underwriting

Luke leads MDA National’s Pricing & Portfolio Underwriting team, overseeing the development and implementation of product strategy and underwriting policies. His work ensures Members continue to benefit from our strong and responsive medical indemnity offerings.

Luke brings expertise in underwriting, professional indemnity, and portfolio leadership. His background spans both domestic and international markets, contributing to product innovation and risk solutions across legal and medical defence sectors. Luke’s collaborative approach and deep market insight support MDA National’s commitment to long-term sustainability and Member protection.

Sarah Thorne

General Manager
Member Experience & Growth

Sarah leads MDA National’s Member Experience and Growth portfolio, driving the organisation’s strategy across growth, propositions, and Member experience. With a strong focus on delivering value for Members and partners, she oversees the development of initiatives that enhance engagement, retention, and relevance in a rapidly evolving market.

Sarah brings deep experience across insurance, healthcare, financial services, and government, having led large-scale transformations and international portfolios. Her background in strategy execution, proposition development, and go-to-market innovation enables her to build high-performing teams and deliver measurable impact, ensuring MDA National remains trusted, contemporary, and Member-focused.

Fiona Wee

General Manager
Corporate Services

Fiona leads MDA National’s Corporate Services portfolio, overseeing Finance, People & Culture, Reinsurance, and Corporate Governance. In this role, she plays a vital part in ensuring the organisation remains financially sound, well-governed, and equipped to support Members now and into the future.

With expertise across financial services and management consulting, Fiona has held previous senior leadership roles, including Chief Financial Officer and Head of Business Performance. She brings a commercially minded, strategic lens to decision-making, underpinned by a strong commitment to organisational sustainability and cross-functional collaboration.