About MJA
About MJA
MJA is an independent commercial, contract and cost assurance partner for infrastructure programmes. We work alongside clients and delivery partners to establish a reliable commercial position and help them make informed decisions.
Our people have operated from Commercial Manager to Commercial Director level and worked within client, contractor and supply chain organisations. That experience shapes how we approach assurance: we understand the delivery pressures behind the numbers and the practical steps needed to strengthen control.
We have particular experience in capital projects, alliances and enterprise delivery models, where several organisations work towards shared outcomes. We design and implement assurance arrangements, review estimates, costs and commercial decisions, and help partners address issues together.
Our quantity surveying, contract management and specialist advisory support strengthens commercial control throughout a project, portfolio or programme.
Our Values
Work together
We work alongside clients, delivery teams and supply chain partners towards shared outcomes. We listen, share knowledge and resolve issues collaboratively, building trust through openness and clear accountability.
Bring clarity and confidence
We combine commercial experience with evidence, analysis and constructive challenge. We make complex cost and contract matters understandable, giving clients a sound basis for decisions while maintaining independence of judgement.
Leave teams stronger
We take responsibility for turning advice into practical improvements. By developing people, strengthening processes and sharing what we learn, we help teams build capability that lasts beyond our involvement.
Our Team
Jonathan Biddy FCIOB
Managing Director
Commercial directorship · Programme stewardship · Assurance design
Jonathan brings more than 35 years’ experience, including operating at Commercial Director level for both clients and contractors, commercially stewarding major infrastructure programmes.
His work spans Hinkley Point C, King’s Cross Redevelopment Programme, Havant Thicket Reservoir and wider transport portfolios.
Alongside delivery leadership, he designs and implements commercial assurance arrangements, with experience at Sizewell C and Southern Renewals Enterprise. He combines strategic oversight with hands-on commercial judgement, supporting integrated teams through complex decisions, change and enterprise delivery.
Mike Harrison
Commercial Leadership and Procurement
Commercial directorship · Procurement strategy · Contract management
Mike brings over 30 years’ commercial leadership experience across UK and international infrastructure.
As Commercial Director with Parsons on Qiddiya in Saudi Arabia, he led commercial and contract management across major infrastructure packages, coordinating commercial, contracts and procurement teams.
His wider experience includes East West Rail, Hinkley Point C and United Utilities. He connects procurement strategy and commercial governance with delivery, working with clients and supply chain partners to manage risk and resolve complex commercial issues.
Andrew Robson MCIOB
Cost Assurance and Commercial Audit
Alliance audit · Start-up assurance · Cost verification
Andrew specialises in independent alliance audit, cost verification and commercial assurance.
As Alliance Auditor for the recently established Midlands Rail Hub, his role includes a defined programme of start-up activities across all business partners to set the alliance up for success.
Building on his REAL Alliance and Hinkley Point C experience, he helps establish clear assurance expectations, review target costs and resolve cost issues, providing alliance boards with evidence-based advice while supporting collaborative delivery.
Danny Jones
Senior Commercial Manager
Major programme delivery · Audit and assurance · NEC commercial management
Danny combines hands-on commercial delivery with audit and assurance experience across major infrastructure programmes.
His work includes Senior Commercial Manager responsibilities delivering major roads programmes for Sizewell C and a recent leading audit and assurance role with Southern Renewals Enterprise.
Drawing on client, contractor and subcontractor experience, including Hinkley Point C and HS2, he brings practical NEC expertise to target costs, forecasting, change management and final accounts, working collaboratively to resolve issues and strengthen commercial control.
Donald Horner FRICS
Supporting Non Executive Director
Strategic advice · Programme assurance · Leadership development
Donald brings senior leadership experience across infrastructure and property, including King’s Cross, Battersea Power Station and Network Rail’s infrastructure advisory commissions.
A Fellow of the Royal Institution of Chartered Surveyors, he supports MJA’s leadership and clients with strategic advice, programme assurance and organisational reviews.
His approach combines constructive challenge with collaborative stakeholder engagement and a practical commitment to developing people.