Who We Are

Jonathan’s passion lies in developing people, especially in management and leadership roles. He is a counselling psychologist and his teaching, research and consulting interests include self-assessment and peer feedback in leadership and management development.

He is chairman and chief consultant of Thornhill Associates. One of his contributions has been to develop the standard Thornhill 360° questionnaires, drawing on his expertise in psychological assessment and experience in management education.

After qualifying as a counselling psychologist, and working with community and church-based organisations for several years, he spent ten years with the National Institute for Personnel Research in Johannesburg, finally as Head of Assessment and Counselling. His next fifteen years were spent as a faculty member at the Graduate School of Business Administration of the University of the Witwatersrand (Wits Business School), where he founded the Management Development Unit and later became director of academic programmes.

In 2004 he joined the Gordon Institute of Business Science (GIBS) of the University of Pretoria as senior lecturer, and in 2011 was appointed Director, a position he held until December 2013.

He left GIBS to devote more time to Thornhill and to the African Management Initiative (AMI – www.africanmanagers.org), which he co-founded and currently chairs. AMI is a social enterprise focused on developing scalable approaches to supporting African managers in excellent performance.

Jonathan is the past chairman of the Association of African Business Schools and of Tomorrow Trust and BizSchool.

He has two sons, two granddaughters and two grandsons.

Martin Cook’s passion is to use creative problem solving and technology to improve people’s lives.

He has a PhD in applied nuclear physics, pioneering a technique to locate diamonds in kimberlite streams using a combination of particle accelerator physics and nuclear medicine. His Masters degree is in string theory, a branch of physics attempting to understand the universe at a fundamental level. He is currently pursuing the commercialisation of his PhD.

Martin worked part time for Thornhill between 2004 and 2014. During that time, he also held positions as a system administrator of a research cluster computer at Wits University, a database developer at a group of HIV/TB clinics and a programme manager at the University of Johannesburg, setting up a new Masters level course in nuclear energy.

After submitting his PhD thesis at the beginning of 2014, he headed up the Thornhill development team until mid 2015. Since then, he has stepped out of day-to-day Thornhill operations, but remains active as a director on the board, and provides occasional input into the development team.

Martin’s biggest joy in life are his daughter (who is, without doubt, the most gorgeous girl on the planet) and his son (who is, without doubt, gearing up to take over the world).

Daphne joined Thornhill Associates in March 2006. She was the admin manager until her appointment as CEO in July 2012. In May 2025, Daphne decided to step into an Operations Manager role. Daphne is a registered counselling psychologist as well as a qualified coach, and she maintains a private practice.

Prior to joining Thornhill, Daphne was self-employed for seven years. During this time her main contracts included conducting research for Africa’s leading publishing group and acting as project manager for P3 Management Consultants. She also spent four years with Hay Management Consultants SA (part of the HayGroup) as senior consulting assistant and support team leader, and Daphne co-ordinated the marketing activities for Hay SA in Africa.

She started her career in 1987 in the IT industry. Daphne was the admin consultant for SilverLine Resources (an IT Contracting, Recruitment and Consulting company) for seven years, before moving to SQL Integrators (now Sybase SA) to support the sales team.

Daphne holds an MA Counselling Psychology (cum laude) from the University of Johannesburg, and completed her internship at the Centre for Psychological Services and Career Development (PsyCaD). She has a BA Hons (Psych) from the University of Johannesburg and a Bachelor of Arts (Psychology and Communication) degree from UNISA. Daphne also holds Myers-Briggs Type Indicator® (MBTI®) International Accreditation, as well as a Brain Based Coaching Certificate from Results Coaching Systems and NeuroLeadership Group.

She is passionate about people development and helping others become all that they can be in every area of their lives. Daphne believes that people can change and volunteers as a co-facilitator for the Alpha course in Leeuwkop Maximum Prison. She thoroughly enjoys travelling and experiencing different cultures, as well as rollercoasters, mountain biking, hiking and reading.

Daphne is married and blessed with a son and a daughter.

Cedric de Beer joined Thornhill Associates in March 2018 as a consultant and coach. Cedric has a life time of experience of establishing organisations, building and leading executive teams and supporting colleagues launch their careers.

From co-founding a rural development agency in the 1970’s, establishing and co-directing a policy research unit at Wits Medical School in the 1980’s, and being the first CEO of a Housing Finance company for fourteen years from 1995, Cedric has brought persistence, imagination and high standards of ethical leadership to the creation of social enterprises in various sectors.   From 2009 he was Director of African Operations for the Soros Economic Development Fund – a New York based social impact investment fund, overseeing investments in logistics, housing, health care and agricultural development. In this capacity he has served as Chairperson of the Boards of companies in Kenya, Tanzania and South Africa.

Cedric brings decades of organisational and governance experience in the public, private and non-profit sectors, and a good understanding of how to get things done in a team. This organisational experience has been complemented by coaching courses with CoachTrax in 2014, and the University of Cape Town Business School in 2016.   Cedric has an Associate Coaching Certificate with the International Coaching Federation (ICF).

Neill Stevenson joined Thornhill Associates in June 2025 as a Consultant, bringing over 30 years of international experience in leadership and organisational development, and strategic consulting across business, nonprofit, and academic sectors.

Prior to joining Thornhill, Neill founded and led several successful ventures, including becoming the largest microcomputer software wholesaler in South Africa. He later pivoted to focus on leadership development with broader impact, negotiating the introduction of the Heriot-Watt Distance Learning MBA to Southern Africa and co-creating a Management Development Programme with the University of Natal.

Neill’s extensive nonprofit experience includes project management and technical advisory roles for USAID-funded consortia supporting orphans and vulnerable children affected by HIV. He has advised the transformation of international NGOs, including co-authoring governance manuals and facilitating board development for a global alliance of 51 organisations across 40 countries.

Neill holds a PhD in Education and Development from Greenwich University and a Master’s in Leadership and Development from the University of KwaZulu-Natal. He is a founder member of COMENSA with over 10,000 documented coaching and mentoring hours.

His consulting work spans strategic planning, corporate governance, mergers and acquisitions, organisational change, and executive coaching. Recent engagements include strategic planning and a governance framework for the World Wildlife Fund’s South West Indian Ocean programme and working with South Bakels, a R2-billion manufacturing firm, on major acquisitions and leadership development.

Neill is passionate about developing human potential at individual, leadership, organisational, and system levels, combining psychological depth and business expertise with practical systems thinking to help leaders navigate complexity and realise their full potential.

He is based in Cape Town and enjoys the opportunity to contribute to Thornhill’s mission of developing high-performing leaders through innovative, tech-enabled learning pathways.

James has worked across sectors, including heavy industry, finance, retail, manufacturing, government, non-government, medical and education. He has consulted with major organisations, such as Nedbank, Investec, UKZN, GIBS, Crawford, Durban Coastal and Mental Health, Foschini, Ackermans, Spar, Bakels, Sapref, Life hospital, St Marys hospital, DA, Durban local government and others, enabling a diverse range of skill development.

He has international consulting experience in the United Kingdom, Israel, Sweden, and Holland, bringing a global perspective on organisational development. James has also lectured and run courses for institutions including the Human Sciences Research Council (HSRC), University of KZN, Varsity College, GIBS and Quality Life.

James is a Director of the Centre for Advanced Management Development (CAMDEV), originally affiliated with the University of KZN. In 2000, he completed an intensive two-year international programme in organisational systems development and leadership through the Gestalt Institute of Cleveland, which involved consulting in five different countries alongside established international organisational consultants.

He holds a Master’s degree in Industrial Psychology from the University of Natal (1989) and an Honours degree in Clinical Psychology (1987). James has completed two internships, one as an industrial psychologist, and the other as a counselling psychologist. This supports his capacity to work effectively with individuals, couples, families, and organisations.

James’ values are linked to quality, meaningful learning, authenticity, and creating tailor-made value-added solutions for his clients. His approach combines psychological insight and practical solutions, helping leaders and teams achieve sustainable and effective performance improvements. Outside of his professional practice, James maintains his wellness through interests including adventure activities, improvisational workshops, martial arts, Pilates, yoga, guitar playing, Argentine tango dancing, hiking, surfing, and team Frisbee.

Marsha is a senior software developer with extensive experience in the IT industry.

She specializes in developing and implementing software solutions tailored to meet specific business needs.

Throughout her career, Marsha has successfully led cross-functional teams in delivering complex projects, utilising various methodologies to enhance workflows and foster collaboration.

Her strong background in software development and IT governance allows her to effectively align software solutions with business objectives.

Keith is a Full-Stack Software Developer with over 15 years of hands-on coding experience. He builds reliable systems that solve real-world problems across various industries, from sports timing to digital marketing, e-commerce, content management systems, and more.

With a lifelong passion for fixing practical things, he has even worked as a bakery technician, repairing all kinds of equipment. In his daily life, he enjoys working on cars and tackling home renovations when his children allow him the time. Keith applies his practical skills and problem-solving abilities to deliver dependable, high-quality software.

Marilyn joined Thornhill in August 2018 as an Administrator bringing experience in administration and customer service, as well as a BA degree in Communication Science and a BA Honours degree in Media Studies.

She is extremely passionate about organising and promoting excellent customer service.

Marilyn enjoys travelling and also loves being outdoors.

Michole joined Thornhill in July 2023 as an Administrator.

Having completed her BA Honours in Psychology, Michole loved delving into the intricate workings of the human mind, exploring various aspects such as behaviours, childhood development, and overall understanding of people. She finds all things Psychology-related very fascinating and strives to learn as much about it as she can. Michole loves to learn new things and is always looking for opportunities to grow further.

Driven by her genuine love for people and children, she finds great joy in discovering and understanding their unique life journeys.

Michole possesses a strong desire to positively impact the lives of others and loves volunteering and serving in her local community.

She adores her family and spending time with those she loves. Outside of her professional pursuits, Michole finds enjoyment in adventuring with her husband, reading, watching movies and series, and playing with her two fur-nephews, Avo and Snoopy.