Independent Commercial Leadership
MBY Consultants was founded on a simple principle: senior commercial support should strengthen the client organisation, not replace its capability.
We support leadership teams when growth, complexity or delivery pressure demands stronger commercial control, while building the internal capability to sustain it.
We work alongside clients to identify where pressure is building, where value may be exposed and what needs to change so the organisation can protect, adapt and grow with greater commercial confidence.
Founded by Mariana Yarnold CMgr FCMI
Mariana Yarnold is a Chartered Manager and Fellow of the Chartered Management Institute with more than 30 years’ experience in commercial, contractual and legal roles across energy, nuclear, defence and infrastructure.
She began her career as an oil and gas lawyer in Argentina, negotiating JOAs, contracts, pipeline agreements and regulatory permits for international energy companies. Since moving to the UK, she has held senior commercial leadership roles at BAE Systems (Submarines), Wood Group, Teekay, JFD, James Fisher Nuclear, the UK National Nuclear Laboratory, Semco Maritime and PBS by Ponticelli. Her work has ranged from negotiating contracts for the Astute class submarine programme to establishing commercial functions in the UK, Sweden and Singapore, and turning around loss-making programmes. She works in English, Spanish and French.
Mariana developed Commercial Architecture™, her theory of how a programme’s commercial arrangements (purpose, authority, incentives and capacity) determine whether it can deliver, and whether its supply chain can invest in what comes next. It is the foundation of the Commercial Architecture Diagnostic® and of all MBY’s work.
Her book, Commercial Architecture: Why good programmes still lose money, is forthcoming. Register your interest
How we work
Every engagement is led by senior practitioners and built around the problem.
We bring together senior commercial practitioners with experience across complex engineering, energy and infrastructure programmes.
Where additional technical, engineering, project delivery or sector-specific capability is needed, we work with a carefully selected network of specialist consultancies and delivery partners. You get the right seniority for the problem, without a junior team learning on your programme.
Our network covers
- Commercial and contract management
- Quantity surveying and cost control
- Project controls and planning
- Procurement and supply chain
- Engineering and technical assurance
Our delivery partners
Why MBY Exists
We believe that commercial expertise should do more than protect a position once a problem has become visible.
Too often, commercial support is brought in narrowly, late or separately from the decisions that shaped delivery from the beginning.
Across energy, nuclear, defence and infrastructure, we have seen how often ambitious organisations are asked to do more than their existing structures were designed to support. The capability is often there, what is missing is the commercial architecture that allows growth to be pursued with confidence.
We believe there is a better way: senior commercial thinking embedded early enough to help leaders understand their exposure, make clearer choices and build the authority, governance and capability needed to carry ambition into delivery.
MBY was created to provide that support without creating dependency. We work alongside our clients to strengthen their organisations for what comes next. Our work is not about taking control, it is about helping our clients hold it with greater confidence.
"From day one MBY set the pace, gave clear direction and put sensible structure around the work, then kept it moving with a steady cadence. They took ownership of the commercial fronts end to end across procurement, AFP, estimating, cost control, EAC and reporting, working directly with the Project Director and the discipline leads so decisions kept moving and risks stayed visible."
Mike Preston - Director - Herne Group
Our Purpose and Values
MBY Consultants exists to help organisations build the commercial strength needed to deliver, compete and grow in complex markets.
Our purpose is to help leaders protect value, adapt to changing demands and grow with greater commercial confidence. We strengthen the commercial architecture that allows organisations to protect value today, adapt with confidence tomorrow and grow without losing control.
Intervention over Observation
We help our clients design governance processes that change outcomes, not just record them.
Sustainable Delivery
We help our clients build delivery models that protect margin, capability and confidence, not just short-term outcomes.
Practical Seniority
We bring judgement shaped by real delivery pressure. Our advice is grounded, executable and tested in practice
Capability Strengthened from Within
We bring senior commercial judgement into the organisation, working with leadership, commercial and delivery teams to sharpen decision-making, strengthen control and build lasting capability.
Commercial Judgement Shaped by Experience
Our experience spans more than 30 years across energy, nuclear, defence, infrastructure and highly regulated delivery environments.
Our work sits at the point where contracts, governance, margin, change, supplier performance and delivery reality meet. We have supported complex programmes and commercial environments where value protection, delivery confidence and practical intervention mattered.
That experience shapes MBY’s approach: clear diagnosis, senior judgement and practical support.