Senior Software Engineer- London

FDM is a global business and technology consultancy seeking a Senior Software Engineer to work for our client within the defence and national security technology sector. This is initially a 12-month contract with very good prospects to extend and will be a hybrid role based in London with a requirement to attend the office at least one day per week and with up to two days’ notice when required.

Our client is a UK based technology company delivering secure unified communications and information sharing platforms for national security and defence users. The role will support development across their existing secure communications platform as well as a new AI enabled decision support product. This is a senior position suited to an engineer who can work with a high degree of autonomy, contribute to technical direction and support less experienced engineers within a small, highly capable team operating in a secure environment.

Responsibilities:

• Designing, developing and maintaining features across secure communications and decision support platforms
• Building and maintaining backend services using C# and related technologies
• Developing and enhancing user interfaces using React
• Contributing to security focused system design when working with highly sensitive data
• Taking ownership of work items, collaborating closely with engineers, product specialists and stakeholders and, at senior level, contributing to mentoring and technical discussions

• Strong commercial experience in backend development using C# and the .NET ecosystem
• Frontend development experience using React or a similar modern JavaScript framework
• Solid understanding of software engineering fundamentals and agile delivery practices
• Experience working in live production environments, ideally within regulated, government or secure systems
• Eligibility for BPSS clearance and preferably SC clearance or willingness to undergo SC clearance
• Minimum of 5 years’ experience in a software engineering role 

FDM is an award-winning global leader in tech and business talent solutions, backed by more than 35 years of industry experience. We have centres across Europe, North America, and Asia-Pacific, and a global workforce of over 2500 employees. FDM has shown exponential growth throughout the years, firmly establishing itself as an award-winning employer, currently listed on the FTSE4Good Index and as a 2026 Financial Times UK ‘Best Employer’. 

Diversity and Inclusion

FDM Group is an equal opportunity employer, and all qualified applicants will receive consideration for employment without regard to race, colour, religion, sex, sexual orientation, national origin, age, disability, veteran status or any other status protected by federal, provincial or local laws.

Why join us

• Career coaching, mentoring and access to upskilling throughout your entire FDM career
• Assignments with global companies and opportunities to work abroad
• Opportunity to re-skill and up-skill into new areas, develop non-linear career paths and build a skillset within your field
• Annual leave and work-place pension